ORIGINAL PAPER. Simulation of a hybrid fermentation separation process for production of butyric acid

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1 Chemicl Ppers 64 (2) (21) DOI: /s ORIGINAL PAPER Simultion of hybrid fermenttion seprtion process for production of butyric cid Mrek Blhušik*, Štefn Schlosser, Ján Mrták Institute of Chemicl nd Environmentl Engineering, Slovk University of Technology, Rdlinského 9, Brtislv, Slovk Republic Received 7 My 29; Revised 14 October 29; Accepted 22 October 29 Simultion of hybrid fermenttion seprtion process for the production of butyric cid (BA) bsed on published dt ws done. A unit consisting of biorector with immobilized cells in the fibrous bed nd of seprtion by pertrction through supported liquid membrnes (SLM) ws considered. Productivities of the unit volume of fixed bed biorector in continuous nd fed-btch fermenttion t ph 5.5 nd 6. were used. Concentrtion of BA in the biorector outlet strem ws ssumed to be in the intervl from.11 to.45. Dt on the pertrction through SLM with phosphonium ionic liquid (IL) nd bulk liquid membrne with trioctylmine (TOA) s crriers were used. A strong increse in the required membrne re ws found for both crriers t the ph of pertrction bove 4. ph vlues of fermenttion nd pertrction should be optimized independently. It is dvntgeous to hve ph of the feed into the pertrction unit of bout 4. Dependences of the membrne re on the pertrction efficiency re nerly liner nd not very shrp, especilly for IL, wht enbles working t the pertrctor efficiency exceeding 9 %. Appliction of phosphonium IL is promising compred to clssicl extrctnt TOA becuse of lower demnd of the membrne re in lrge intervl of BA concentrtions in the pertrctor feed. c 29 Institute of Chemistry, Slovk Acdemy of Sciences Keywords: extrctive fermenttion, butyric cid, pertrction, supported liquid membrne, ionic liquid, trioctylmine Introduction Continuous removl of product in fermenttion is n effective wy of reching high substrte utiliztion t resonble production rtes by decresing the product inhibition (Htzinikolou & Wng, 1992; Schlosser, 2, 29; Schlosser et l., 25; Wu & Yng, 23). Fermenttion of butyric cid (BA) by Clostridium butyricum nd its in situ solvent extrction by tertiry mines dissolved in oleyllcohol nd by pure oleyllcohol were tested previously (Vndák et l., 1997; Zigová et l., 1999). A hybrid fermenttion extrction process for the production of BA ws simulted by Htzinikolou nd Wng (1992). Only equilibrium prtitioning of BA into oleyllcohol ws considered in this simultion. Conversion of citric cid to itconic cid in n extrctive membrne biorector with supported liquid membrne (SLM) ws studied in the pper by Bressler nd Brun (2). Fermenttion cn be crried out in biorector with free or immobilized microorgnisms or in column biorector with immobilized microorgnisms operting in prllel circultion loops in repeted fedbtch or continuous opertion s. BA cn be recovered from the fermenttion broth by solvent extrction, membrne bsed solvent extrction, nd pertrction. Optimum ph of broth in continuous nd fedbtch fermenttion processes in the biorector for BA production with immobilized cells in fixed bed column is bout 5.5 nd 6. with the biorector productivities *Corresponding uthor, e-mil: Mrek.Blhusik@stub.sk Presented t the 36th Interntionl Conference of the Slovk Society of Chemicl Engineering, Ttrnské Mtlire, My 29.

2 214 M. Blhušik et l./chemicl Ppers 64 (2) (21) ph djustment Substrte solution 1 Nitrogen C3 5 1 Fermenttion broth bleed 11 C1 ph djustment 3 6 PT Fresh stripping solution 8 2 B C2 7 9 Loded stripping solution Fig. 1. Schemtic flow sheet of hybrid fermenttion seprtion process for production of butyric cid with immobilized biomss. C1 fermenter continer, B biorector with supported biomss, C2 continer of broth for ph djustment, PT hollow fiber pertrctor with SLM, C3 continer of len broth with ph djustment, 1 concentrted substrte solution, 2 input into the biorector, 3 biorector output, 4 recycled broth, 5 broth entering the pertrction loop, 6 cid for ph djustment, 7 feed into the pertrctor, 8 fresh stripping solution, 9 loded stripping solution, 1, 12 len fermenttion solution, 11 fermenttion broth bleed, 13 recycled len fermenttion solution with djusted ph, 14 mmoni solution for ph djustment. of bout 1.11 h 1 nd 1. h 1, nd with finl BA concentrtions in the fermenttion solution of.11 nd.45, respectively (Wu & Yng, 23). BA ws extrcted into solvent composed of trilkylmine nd oleyllcohol in the hollow fiber contctor. The bove mentioned vlues of ph in the fermenttion process re not fvorble forextrctionorpertrction becuse t ph 5.5 only 6 % of BA is undissocited, i.e. in the form which cn be effectively extrcted nd trnsported through the membrne (Schlosser et l., 25). Thus, ph djustment in the feed flow to the pertrction unit cn be of importnce. Pertrction of BA in contctor with lyered bulk liquid membrne (BLM) ws studied in the pper by Schlosser nd Sbolová (1999). Membrne bsed extrction nd stripping of BA in hollow fiber contctors with the cross flow of phses ws investigted by Schlosser nd coworkers (Kertész & Schlosser, 25; Sbolová & Schlosser, 21; Schlosser et l., 21b). Dt on solvent extrction of BA (Mrták & Schlosser, 28) nd lctic cid (Mrták & Schlosser, 26) using phosphonium ionic liquids (IL) show the potentil of IL to be pplied in the seprtion of cids. Pertrction of BA through flt sheet SLM with ionic liquid (IL) ws studied by Mrták nd Schlosser (27), nd pertrction through bulk liquid membrne (BLM) with trioctylmine (TOA) in hollow fiber contctor by Schlosser (2) nd Schlosser et l. (21b). Results on the pertrction of lctic cid through SLM with phosphonium ionic liquid hve been presented recently (Mrták et l., 28). Influence of bsic process prmeters on the fermenttion pertrction (F-PT) process performnce were nlyzed bsed on vilble published dt on fermenttion (Wu & Yng, 23). Dt on pertrction through flt sheet SLM with ionic liquid (IL) (Mrták & Schlosser, 27) nd on pertrction through BLM with trioctylmine (TOA) in hollow fiber contctor (Schlosser, 2; Schlosser et l., 21b) were used in the simultion. Competitive trnsport of minerl cid hs negtive influence on the pertrction rte of orgnic cids through the lyered SLM (Kubišová et l., 1997; Sbolová et l., 1997; Schlosser et l., 21). This influence is less pronounced for the BA trnsport through liquid membrne (Sbolová et l., 1997) thn for the lctic cid pertrction (Kubišová et l., 1997) using TOA s the crrier. Theimofthepresentedworkwsthesimultion of the hybrid F-PT process for the production of BA nd the estimtion of the influence of bsic process prmeters on its performnce. Hybrid F-PT process Theoreticl Bsic concept of the F-PT process is the removl of product, BA, to prevent biosynthesis inhibition by its product nd to prolong the biomss lifetime. There re two possible opertion s of the F-PT process: continuous nd fed-btch. The flow sheet of the process is shown in Fig. 1. In the continuous of opertion, the substrte solution 1, len broth from pertrction 13, nd recycled fermenttion broth from

3 M. Blhušik et l./chemicl Ppers 64 (2) (21) 215 the biorector 4 re mixed in the fermenter continer C1 to form the feed into the biorector B, which is column with immobilized cells, e.g. in fibrous bed (Wu & Yng, 23). A smll prt of the fermenttion solution in the rector outlet cn be optionlly recycled. ph of the fermenttion solution contining the product is t level fvorble for the fermenttion, which cn be on the other hnd unfvorble for the pertrction. Thus, ph of strem 5 cn be djusted in the continer C2. The fermenttion solution fter the ph djustment (strem 7) is fed into the pertrctor PT with SLM. A prt of the processed fermenttion solution is continuously removed s the fermenttion broth bleed 11 to keep the slt concentrtion in the unit t n cceptble level. Slts re generted due to the ph djustment in the fermenter nd in the pertrction loop keeping the optimum ph. After tht, ph vlue of the len fermenttion solution 12 is djusted bck to the level fvorble for the biosynthesis by n ddition of bse to the continer C3 nd broth 13 is returned bck to the fermenter continer C1. In the fed-btch opertion, the fermenter consists of continer C1 nd biorector B, where the product is ccumulted. At the beginning of every opertion cycle, the fermenter is filled with the len broth from previous btch 13 nd with concentrted substrte solution 1. The fermenttion solution in continer C1 is recycled through biorector B until the product concentrtion reches its finl vlue. At the end of ech cycle, the content of the fermenter tnk C1 is pumped into tnk C2, where its ph cn be djusted. Then, the broth is continuously fed into pertrctor PT. Len broth from the pertrction unit is collected in tnk C3 nd fter the ph djustment it is returned into the fermenter continer C1. Simultion l Simultion l of the F-PT process is bsed on mss blnce equtions of the process, kinetics of biosynthesis, nd mss trnsfer equtions for the estimtion of the membrne re in the hollow fiber contctors with SLM. The lck of dt concerning the biosynthesis hd to be considered when formulting the simultion l. Productivity of the biorector with immobilized cells is supposed to be constnt nd dt from the pper by Wu nd Yng (23) were used. Continuous fermenttion Mss blnces in the continuous opertion re in the form of molr nd volumetric flows. In the formultion of these equtions, stedy stte conditions were supposed. It ws lso supposed tht the chnges of volumetric flow rtes in strems, V, due to only smll composition chnges in the biorector nd smll volumes of cid nd bse dditions in ph djustment, nd eqution V 2 = V 5 = V 7 = V 1 (1) holds. Numbers in the indices refer to the strem numbers s shown in Fig. 1. Prt of the fermenttion solution hs to be continuously removed in order to mintin constnt level of slt(s) content nd the medium volume in the unit. The rtio of volumetric flow rtes of the bleed strem 11 nd the pertrctor output 1 is defined s φ b = V 11 V 1 (2) Mss blnce of BA in the unit in stedy stte cn be written s follows ṅ prod =ṅ 9 +ṅ 11 (3) where ṅ prod is the molr flow rte of BA produced in the biorector, ṅ 9 is the molr flow rte of BA isolted by pertrction in strem 9, nd ṅ 11 is the molr flow rte of BA in the fermenttion broth bleed, strem 11. Molr flow rte of BA in strem 9, ṅ 9,cnbeexpressed in terms of the pertrction yield, η, ndmolr flow rte of BA t the inlet to the pertrction unit, ṅ 7,s ṅ 9 =ṅ 7 η (4) Similrly, n eqution cn be written for the clcultion of the BA molr flow lost in the fermenttion broth bleed, ṅ 11, ṅ 11 =ṅ 7 (1 η) φ b (5) Molr flow, ṅ 7, cn be expressed ssuming the mximum nlytic molr concentrtion of BA (undissocited plus dissocited BA) in the rector outlet strem, c,mx ṅ 7 = c,7 V7 = c,mx V5 (6) where c is the nlytic molr concentrtion of BA nd numbers in the indices refer to the strem numbers s shown in Fig. 1. Combining Eqs. (3) (6), the reltion for ṅ prod cn be derived ṅ prod = c,mx V5 [η +(1 η) φ b ] (7) Since the product formtion rte, ν BA, in the biorector is supposed to be constnt t concentrtions bellow c,mx, the right hnd side of Eq. (7) is ṅ prod = ν BA V bior (8) Combining Eqs. (8) nd (9), volumetric flow rte

4 216 M. Blhušik et l./chemicl Ppers 64 (2) (21) of the broth trough the biorector cn be expressed V 5 = V bior ν BA c,mx [η +(1 η) φ b ] (9) Consumptions of minerl cid nd bse, H 2 SO 4 nd NH 3, respectively, in the pertrction loop were clculted ccording to simple equtions, s the full dissocition of these chemicls ws supposed nd ll other cid-bse equilibri were neglected. Since the fermenttion solution contins wek butyric cid (pk BA = 4.82) nd its slt, it cts s buffer solution. The consumption of H 2 SO 4 for djustment of the ph of the fermenttion solution, ph ferm,tothelevel needed in the pertrction unit, ph 7,isclculteds sum of the mount of cid required for the tretment of solution without buffer properties nd the mount needed to exchnge ctions of BA slt for hydrogen ions. Anlogiclly, the consumption of bse is clculted, considering the chnge in the mount of BA in the pertrctor outlet solution expressed with respect to the BA yield, η, ṅ H2SO 4 = 1 2 V [( ) 5 1 ph ferm 1 ph 7 + (1) ( 1 ph 7 1 ph )] 5 +c,mx 1 ph 7 +1 pk BA 1 ph 5 +1 pk BA ṅ NH3 = V [( ) 12 1 ph ferm 1 ph 7 + c,mx (1 η) ( 1 ph 7 1 ph )] 5 1 ph 7 +1 pk BA 1 ph 5 +1 pk (11) BA where V 12 cn be expressed using Eqs. (1) nd (2) s follows Repeted fed-btch fermenttion V 12 =(1 φ b ) V 5 (12) Mss blnces in the fed-btch opertion re in the form of moles nd volumes. The equtions were formulted for the time of one cycle, t C.Itisdvntgeous to define three rtios concerning the process. Volume rtio of biorector B, V bior,tothewhole fermenter, V ferm, is defined s φ ferm = V bior V ferm (13) Volume of the fermenter in the fed-btch opertion is clculted s sum of volumes of the biorector nd the content of the fermenter continer C1 V ferm = V C1 + V bior (14) Volume rtio of the broth removed from the fermenter, V 5, t the end of every fermenttion cycle to the totl volume of the fermenter (A prt of the biorector volume is occupied by biomss nd support nd lso prt of the fermenttion broth hs to remin in the fermenter to hve the biomss submerged) φ f = V 5 V ferm (15) The rtio of broth volume removed s bleed to the totl volume of the fermenttion solution processed by pertrction is defined s φ b = V 11 V 1 (16) Mss blnce of BA for one cycle cn be written similrly to Eq. (3) s n prod = n 9 + n 11 (17) where n prod re moles of BA produced in the fermenter during one cycle, n 9 re moles of BA seprted by pertrction in strem 9, nd n 11 re moles of BA removed in the broth bleed in every cycle. Similrly to Eq. (4) for the continuous opertion, the reltion for n prod cn be derived n prod = n 7 [η +(1 η) φ b ] (18) The mount of BA in the broth removed from the fermenter during one cycle, n 7, cn be expressed in reltion to the totl mount of BA in the fermenter t the end of ech cycle using Eq. (15) n 7 = c,mx V ferm φ f = n ferm φ f (19) where n ferm is the totl mount of BA in the fermenter nd c,mx is the mximum concentrtion of BA in the fermenter t the end of ech cycle. Combining Eqs. (15), (17), nd (18), the molr mount of BA produced in one cycle cn be expressed s n prod = c,mx V ferm φ f [η +(1 η) φ b ] (2) At constnt productivity, ν BA, of the biorector, the left hnd side of Eq. (2) cn be expressed by the reltion n prod = ν BA V bior t C = ν BA V ferm t C φ ferm (21) The cycle time cn be expressed combining Eqs. (2) nd (21) t C = c,mxφ f ν BA φ ferm [η +(1 η) φ b ] (22) Since the pertrction unit works exctly s in the continuous, the volumetric flow rte of the fermenttion solution in the pertrction prt is defined

5 M. Blhušik et l./chemicl Ppers 64 (2) (21) 217 by the volume of the solution processed in the pertrction unit which follows from Eq. (15) nd the time of the cycle, t C, V 7 = V fermφ f (23) t C Combining Eqs. (13), (22), nd (23), volumetric flow rte of the broth in the pertrction unit cn be expressed V 7 = V ferm ν BA φ ferm c,mx [η +(1 η) φ b ] = V bior ν BA c,mx [η +(1 η) φ b ] (24) which is the sme eqution s Eq. (9) in the continuous opertion. The consumption of chemicls is clculted similrly to the continuous opertion, Eqs. (1) nd (11), n H2SO 4 = 1 2 V [( ) 5 1 ph ferm 1 ph 7 + (25) ( 1 ph 7 1 ph )] 5 +c,mx 1 ph 7 +1 pk BA 1 ph 5 +1 pk BA [( ) n NH3 = V 12 1 ph ferm 1 ph 7 + c,mx (1 η) ( 1 ph 7 1 ph )] 5 1 ph 7 +1 pk BA 1 ph 5 +1 pk (26) BA where Membrne re V 12 = V 5 (1 φ b ) (27) Estimtion of the membrne re needed in the hollow fiber contctor ws crried out ccording to the method suggested for membrne bsed solvent extrction by Kertész nd Schlosser (25). Mss-trnsfer of BA in the contctor differentil element cn be expressed s dṅ = K p επd v N(c F c FR )dz (28) where K p is the overll mss-trnsfer coefficient, ε is the porosity, d v is the inner dimeter of the hollow fiber in the contctor, N is the number of hollow fibers in the contctor, c F is the concentrtion of undissocited BA (BAH) in the feed, nd c FR is the equilibrium concentrtion of BAH in the feed relted to its concentrtion in the stripping solution. The vlue of c FR is supposed to be negligible due to high excess of bse in the stripping solution. The integrl form of this eqution for j-th segment, in which the overll mss-trnsfer coefficient is supposed to be constnt, cn be written s ṅ j = K p,j εa g,j c Fj,ls (29) where c Fj,ls is the men logrithmic concentrtion of undissocited BA in the feed phse nd A g,j is the geometric surfce re, respectively, both in the j-th segment of the pertrctor. c Fj,ls in ny segment of the contctor cn be clculted using the men logrithmic vlue of the nlyticl BA concentrtion, c F,ls, nd the ph vlue of the solution in this segment 1 ph 7 c Fj,ls = 1 pk c,ba 1 ph Fj,ls (3) 7 The overll membrne re of the pertrctor is clculted s sum of surfce res estimted for ll elements of the contctor using Eq. (29). The rtio of the inlet nd outlet concentrtions of BA in every element is supposed to be constnt nd it cn be clculted from the BA concentrtions t the pertrctor inlet nd outlet, s follows ( ) 1 c F,n+1 cf,in n = (31) c F,n c F,out Input dt into the simultion l The following input dt for both opertion s were used in the simultion l, if not otherwise stted. Continuous fermenttion φ r = (no recycle of broth from biorector), φ b =.1 (supposed), c,mx =.11kmolm 3 (1kgm 3 ). The vlue of c,mx ws estimted from the dt for BA concentrtion of bout 5 kg m 3 in the biorector feed (Wu & Yng, 23). Estimtion of the flow rte of broth ws bsed on supposed velocity of the feed of 2. cm s 1 in extrctor fibers. ph ferm =ph 5 =5.5, =1.11kmolm 3 h 1 (98.27 kg m 3 h 1 ) this vlue of productivity of unit volume of the biorector ws estimted from the productivity of 7.37 kg m 3 h 1 referred to the whole broth volume t ph ferm =5.5 presented in the pper by Wu nd Yng (23). Repeted fed-btch fermenttion φ ferm =.7, φ f =.93, φ b =.1 (supposed), c,mx =.45kmolm 3 (4 kg m 3, mximum concentrtion t the end of fermenttion cycle (Wu & Yng, 23)), ph ferm =ph 5 =6.,=1.kmolm 3 h 1 (88. kg m 3 h 1 ) this vlue of productivity of unit volume of the biorector ws estimted from the productivity of 6.7 kg m 3 h 1 referred to the whole broth volume t ph ferm = 6 presented by Wu nd Yng (23). Membrne re clcultion Membrne re in the HF contctor with SLM ws clculted by short cut method similr to the

6 218 M. Blhušik et l./chemicl Ppers 64 (2) (21) method used for membrne re estimtion in cse of membrne bsed solvent extrction proposed by Kertész nd Schlosser (25). Number of segments chosen for the estimtion of membrne surfce re ws ten nd the support porosity ssumed ws ε =.4. Experimentl vlues of the overll mss-trnsfer coefficient for pertrction of BA through SLM with solution of ionic liquid Cyphos IL-14 in dodecne (.72 ) (Mrták & Schlosser, 27) were used. The equipment contined PTFE microporous membrne with the thickness of 66.4 µm, nd the porosity of.7. The feed nd stripping solutions flowed in spirl chnnels on both sides of SLM with the hydrulic dimeter of.42 mm (Kertész et l., 24); these chnnels re similr to those in hollow fibers. The feed velocity ws in the intervl of cm s 1. Experimentl dt on K p vs. the BA men concentrtion in the feed, c F,ls, in the intervl from.14 to.454, were correlted by the following eqution (R 2 =.982) K p 1 6 =(.8978 c F,ls ) 1/ (32) For TOA, n empiricl eqution for the concentrtion dependence (in the intervl from.19 kmol m 3 to.52 ) of the overll mss-trnsfer coefficient in pertrction of BA through bulk liquid membrne in hollow fiber contctor, bsed on dt published in ppers by Schlosser (2) nd Schlosser et l. (21b), ws used (R 2 =.998) A g /V bior, (m -1 ) J BAmen 1 6, (kmol m 2 s -1 ) ph ph 7 Fig. 2. Influence of ph of the feed to the pertrction unit on the membrne surfce re per unit volume of the biorector () nd on the men vlue of the BA flux through SLM (b) in the hybrid F-PT process with continuous fermenttion. SLM with IL (squres) nd TOA (circles). Vlues of the BA yield in pertrction (η) were.9 (full symbols) nd.8 (empty symbols). b K p 1 6 =4.3c 3 F,ls +5.15c2 F,ls +2.94c F,ls +1.94(33) Experimentl equipment contined two bundles of polypropylene hollow-fibers Celgrd X-1 (Celgrd, USA), with the wll thickness of 64 µm, inner dimeter of.2 mm, nd porosity of 3 %. The feed solution velocity ws kept t 5.5 cm s 1. Competitive trnsport of minerl cids in solvents with ionic liquids should be studied in future to tke into ccount this effect especilly in cses when ph djustment by minerl cids is used. In the first pproximtion, in the presence of minerl cid used for the djustment of ph, 8 % of the K p vlues for IL nd TOA clculted by Eqs. (32) or (33) were used in the estimtion of the membrne surfce re. Results nd discussion Continuous fermenttion With the incresing ph of the feed into the pertrction unit bove 4., the specific membrne surfce re required for both IL nd TOA crriers to chieve the specified pertrction efficiency s shown in Fig. 2 shrply increses. Correspondingly, t this ph, the vlue of the men permete flux strts to de- crese (Fig. 2b). According to ph dependences shown in Fig. 2, trnsport properties of SLM with IL re much more fvorble to be pplied in the continuous opertion, especilly t higher vlues of ph 7, ner to ph ferm. Specific consumption of sulfuric cid needed to chieve ph in the feed to pertrction unit (ph 7 ) from ph ferm increses lmost linerly below ph 5.5 (ph ferm ), until it reches the vlue of pproximtely 4. Specific consumption of sulfuric cid decreses with the incresing yield of BA in pertrctor (Fig. 3). This is cused by the buffer properties of the solution of BA nd its slt. Below the ph vlue of 4, the mjority of BA is undissocited, ny further minerl cid ddition decreses the solution ph without buffering. The sme trend ws observed for the specific consumption of mmonium hydroxide used to djust ph of the broth bck to ph ferm (Fig.3b).AtpH 7 =4nd9% yield of BA in pertrction unit, specific consumption of sulfuric cid nd mmonium hydroxide ws bout.5 mol per one mol of produced BA nd.2 mol per one mol of produced BA, respectively. SLM trnsport properties in the presence of both IL nd TOA crriers enble high yield of the product, of bout 9 %,

7 M. Blhušik et l./chemicl Ppers 64 (2) (21) 219 n H2SO4 /n BA, A g /V bior, (m -1 ) ph pH 7 6 n H2SO4 /n BA, ph 7 J BAmen 1 6, (kmol m -2 s -1 ) ph 7 b Fig. 3. Influence of ph of the feed to the pertrction unit on the specific consumption of sulfuric cid needed to chieve ph 7 from ph ferm () nd the specific consumption of mmonium hydroxide to djust ph 12 of the len broth bck to ph ferm (b) in the hybrid F-PT process with continuous fermenttion. Vlues of the BA yield in pertrction (η) were.5 (full squres),.7 (empty squres),.8 (full circles), nd.9 (empty circles). Fig. 4. Influence of the ph of the feed to the pertrction unit on the membrne re needed () nd on the men vlue of the BA flux through the membrne (b) in the hybrid F-PT process with fed-btch fermenttion. SLM with IL (squres) nd TOA (circles). Vlues of the BA yield in pertrction (η) were.9 (full symbols) nd.8 (empty symbols). without ny excessive increse of the membrne re needed. Fed-btch fermenttion Similr dependences were observed lso in the hybrid process with the fed-btch fermenttion. Dependence of the membrne surfce re on ph is shown in Fig. 4. Different trnsport properties of the crriers resulted in more fvorble men fluxes of BA t ph 7 below 4.5 for TOA (Fig. 4b). Membrne re needed for both crriers is lower in the process with fed-btch fermenttion compred to the process with continuous fermenttion. This is due to much higher concentrtion of BA in the feed to the pertrction unit in the fed-btch process nd, ccordingly, to higher driving force in the pertrction unit. Specific consumption of sulfuric cid nd mmoni is slightly lower in the process with continuous fermenttion thn in tht with fed-btch fermenttion due to lower ph of the fermenttion broth, s shown in Fig. 5. Similrly s in the continuous opertion, the yield of 9 % of BA from the pertrction cn be chieved, especilly for ph 7 equl to 4.5 nd lower. Comprison of F-PT process opertion s As shown in previous subsections, the vlues of membrne surfce re for both crriers re fr more fvorble nd the consumption of chemicls is slightly higher for the fed-btch opertion compred to the process with continuous fermenttion. This refers to much lower vlues of BA concentrtion nd ph t the biorector outlet in the continuous opertion compred to their finl vlues in the fermenttion solution fter the synthesis cycle in the fedbtch fermenttion process. Smll difference between the productivities of immobilized biomss in different opertion s, of bout 1 %, suggests tht the concentrtion of BA in the fermenttion solution t the outlet of the biorector could be in cse of the continuous opertion higher thn.11, without significnt decrese in the biosynthesis rte. This would significntly decrese the membrne re needed in the pertrctor unit, s shown in Fig. 6. ph dependences of men BA flux in Fig. 6b show tht the improvement due to higher concentrtion of BA t the pertrctor inlet t ph = 4 nd lower is higher for TOA thn for IL.

8 22 M. Blhušik et l./chemicl Ppers 64 (2) (21) n H2SO4 /n A g /V bior, (m -1 ) n NH3 /n pH pH 6 7 Fig. 5. Influence of ph of the feed to the pertrction unit on the specific consumption of sulfuric cid needed to chieve ph 7 from ph ferm () nd on the specific consumption of mmonium hydroxide to djust ph of the len broth bck to ph ferm (b) in the hybrid F-PT process with fed-btch fermenttion. Vlues of the BA yield in pertrction (η) were.5 (full squres),.7 (empty squres),.8 (full circles), nd.9 (empty circles). b J BAmen 1 6, (kmol m -2 s -1 ) ph ph 7 6 Fig. 6. ph dependences of the membrne re per unit volume of the biorector needed () nd the men vlue of the BA flux through the membrne (b) in pertrction unit for the hybrid process with continuous fermenttion. SLM with IL (empty symbols) nd TOA (full symbols). Vlues of the output concentrtion of BA from the biorector, c,mx, were.11kmolm 3 (1 kg m 3, circles),.17,(15kgm 3,tringles), nd.23 (2 kg m 3,squres). b However, higher difference between the BA concentrtions t the inlet nd outlet of the biorector, which should be chieved in one pss through the biorector, mens drop of ph without the possibility to djust it, which results in decresed rection rtes. Possibly, more columns of immobilized biomss in series with the ph djustment in-between cn be employed. For deeper nlysis, more informtion on the biosynthesis kinetics with respect to substrte nd product concentrtion s well s to the ph of the fermenttion solution is required. Different trnsport properties with respect to the concentrtion of the undissocited form of BA re obvious compring the membrne res for IL nd TOA crrier. In wide rnge of the studied conditions for both opertion s, the membrne re needed is lower for IL thn for TOA. For unit producing 1 t of BA per dy in the continuous opertion (.11 of BA t the biorector outlet), membrne res in the contctors needed t η =.9forSLM with IL nd TOA t ph 7 =ph ferm = 5.5 were 3315 m 2 nd 2342 m 2, respectively, nd t ph 7 =4.they were 164 m 2 nd 3938 m 2, respectively. However, t higher concentrtions of BA in the fermenttion so- lution (.45 ) in the process with fed-btch fermenttion t ph 7 = 4., the membrne re needed in the pertrctor unit t η =.9 ws lower for TOA thn for IL (584 m 2 nd 755 m 2 ). This suggests tht the choice of the proper crrier for this ppliction should be mde considering the ctul opertion conditions in the process. Conclusions Simultion of the hybrid fermenttion pertrction process for the production of butyric cid shows tht ph of the fermenttion nd pertrction solutions should be optimized independently. It is dvntgeous to djust ph of the feed into the pertrction unit to bout 4. for both IL nd TOA crriers. In cse of the continuous opertion, the decrese of ph t the inlet to the pertrctor from 5.5 to 4 cuses the reduction of the membrne re by 52 % for IL nd by 81 % for TOA. Selection of proper crrier, IL or TOA, in the supported liquid membrne should be mde ccording to ctul opertion conditions of the fermenttion process becuse of different trnsport properties of these

9 M. Blhušik et l./chemicl Ppers 64 (2) (21) 221 crriers in respect to the concentrtion of undissocited BA. While t lower concentrtions, IL is more pproprite crrier, t higher BA concentrtions, of bout 4 kg m 3 nd ph equl to 4., the membrne re needed is lower when using TOA s the crrier. However, development of new ILs nd membrne formultions, in combintion with their potentilly lower toxicity cn further enhnce their ppliction potentil. With the incresing concentrtion of BA in the feed into the pertrctor, the requirements for membrne surfce re decrese. In this respect, the F-PT process in the fed-btch is more beneficil with only slight increse in the chemicls consumption due to higher vlue of ph of the fermenttion solution. However, possible increse of the BA concentrtion in the continuous opertion in connection with the development of new strin nd the use of series of biorectors with ph djustment between them would decrese the membrne re needed mking this opertion more interesting. Symbols A g geometric membrne surfce re m 2 c nlyticl molr concentrtion of BA c,i nlyticl molr concentrtion of BA (undissocited nd dissocited) in i-th strem c,mx mximum molr nlyticl concentrtion of BA in fermenter chieved t the end of the synthesis cycle in fed-btch fermenttion or concentrtion of BA t the outlet of biorector in continuous opertion c F molr concentrtion of BAH in feed c FR equilibrium molr concentrtion of BAH in feed relted to its concentrtion in the stripping solution c F,ls logrithmic men molr concentrtion of BAH in the segment of pertrctor in the feed solution d v inner dimeter of hollow fiber in contctor m J BA,men men molr flux of BA in pertrctor kmol m 2 s 1 K p overll mss trnsfer coefficient m s 1 N number of hollow fibers in pertrctor n i molr mount of BA in i-th strem t the end of the cycle in fed-btch opertion kmol ṅ i molr flow of BA in i-thstremincontinuous opertion kmol s 1 n prod molr mount of BA produced in biorector during one cycle in fed-btch opertion kmol ṅ prod molr mount of BA produced in biorector per unit time in continuous opertion kmol s 1 n H2SO 4 molr mount of H2SO4 consumed in the time of one cycle in cse of fed-btch opertion mol ṅ H2SO 4 molr flow of H2SO4 in continuous opertion mol h 1 n NH3 molr mount of NH3 consumed in the time of one cycle in fed-btch opertion mol ṅ NH3 molr flow of NH3 in continuous opertion mol h 1 ph ferm ph in fermenter ph i ph in i-th strem ph pertr ph in strem 7 (in the inlet of pertrctor) pk BA negtive vlue of logrithm of the dissocition constnt of BA t C time of one cycle in fed-btch process h u F velocity of feed in fibers of pertrctor m s 1 V bior volume of biorector m 3 V cont volume of continer of the fermenter m 3 V ferm volume of fermenter, Eq. (14) m 3 V i volume of fermenttion solution which flows in i-thstreminthetimeofonecycle in fed-btch opertion m 3 V i volumetric flow rte of fermenttion solution in i-th strem m 3 h 1 ε η ν BA membrne porosity yield of BA in pertrction, defined s rtio of molr flows of BA t the outlet of stripping solution from pertrctor nd t the fermenttion solution inlet into pertrctor biomss productivity per unit of volume of the biorector h 1 φ b rtio defined by Eq. (2) φ f rtio defined by Eq. (15) φ ferm rtio defined by Eq. (13) φ r recircultion rtio of biorector outlet in cse of continuous opertion, defined s the rtio of volumetric flow rte in 4th nd 5th strem Acknowledgements. Support of the Slovk Grnt Agency VEGA 1/876/8 is cknowledged. References Bressler, E., & Brun, S. (2). Conversion of citric cid to itconic cid in novel liquid membrne biorector. Journl of Chemicl Technology nd Biotechnology, 75, DOI: 1.12/(SICI) (21)75:1<66::AID-JCTB176> 3..CO;2-U. Htzinikolou, D. G., & Wng, H. Y. (1992). Extrctive fermenttion systems for orgnic cids production. The Cndin Journl of Chemicl Engineering, 7, DOI: 1.12/cjce Kertész, R., & Schlosser, Š. (25). Design nd simultion of two phse hollow fiber contctors for simultneous membrne

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