Saccharification Of Sugarcane Bagasse Research Articles

Optimization of simultaneous saccharification and fermentation in bioethanol production from sugarcane bagasse hydrolyse by Saccharomyces cerevisiae BTCC 3 using response surface methodology

The response surface method (RSM) was used to investigate the effects of bioethanol fermentation parameters, including sugarcane bagasse concentrations (0-5 % (w/v), enzyme types (cellulase and hemicellulase), enzyme concentrations (0-1 FPU/g biomass), medium pH, and incubation period. Bioethanol production was conducted by simultaneous saccharification and fermentation (SSF) of sugarcane bagasse hydrolyse using Saccharomyces cerevisiae BTCC 3. The experiment results showed that the maximum bioethanol production by using the SSF method was the same as RSM prediction. The optimum conditions for bioethanol production were 5% (w/v) of sugarcane bagasse, a mixture of cellulase and hemicellulase at 1 FPU/g of sugarcane bagasse for each enzyme, pH medium 6.0, and fermentation period 72 hours. The bioethanol yield of 2.43 g/L was obtained under these conditions.

Alternative Low-Cost Additives to Improve the Saccharification of Lignocellulosic Biomass.

A potential strategy to mitigate problems related to unproductive adsorption of enzymes onto lignin during the saccharification of lignocellulosic biomass is the addition of lignin-blocking agents to the hydrolysis reaction medium. However, there is a clear need to find more cost-effective additives for use in large-scale processes. Here, selected alternative low-cost additives were evaluated in the saccharification of steam-exploded sugarcane bagasse using a commercial enzymatic cocktail. The addition of soybean protein, tryptone, peptone, and maize zein had positive effects on glucose release during the hydrolysis, with gains of up to 36% when 8% (w/w) soybean protein was used. These improvements were superior to those obtained using bovine serum albumin (BSA), a much more expensive protein that has been widely reported for such an application. Moreover, addition of soybean protein led to a saving of 48h in the hydrolysis, corresponding to a 66% decrease in the reactor operation time required. In order to achieve the same hydrolysis yield without the soybean additive, the enzyme loading would need to be increased by 50%. FTIR spectroscopy and nitrogen elemental analysis revealed that the additives probably acted to reduce unproductive binding of cellulolytic enzymes onto the lignin portion of the sugarcane bagasse.

Development of an environmental-benign process for efficient pretreatment and saccharification of Saccharum biomasses for bioethanol production

Abstract Saccharum biomasses (Saccharum munja and sugarcane bagasse) were subjected to different physical, chemical and biological pretreatment methods. Physical pretreatment of lignocellulosic biomasses was carried out by using steam treatment and microwave. Chemicals pretreament of lignocellulosic biomasses were optimized by using different chemicals like alkalies and acids. Among all chemicals, ammonia treatment significantly removed lignin (approx. 77%) and removed high amount of phenolic compounds and enhanced saccharification of Saccharum munja and sugarcane bagasse. Laccase pretreatment significantly removed lignin and enhanced the reducing sugar production by 2-fold corresponding to approx. 60% saccharification of pretreated biomass as compared to other methods. Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) showed the removal of lignin due to pretreatments. Bio-ethanol production carried out using hydrolysate of both substrates by Saccharomyces cerevisiae and Pichia stipitis at 30 °C and 150 rpm after 72 h produced high amount of ethanol (25.06 g/L and 24.56 g/L for S. munja and sugarcane bagasse, respectively). Enzymatic hydrolysate fermented by the co-culture of S. cerevisiae and P. stipitis produced 30.78 g/L and 31.56 g/L of bioethanol from S. munja and sugarcane bagasse hydrolysate, respectively. Results indicated enhanced bioethanol production by co-culturing of pentose and hexose fermenting yeasts.

Catalytic properties of cellulases and hemicellulases produced by Lichtheimia ramosa: Potential for sugarcane bagasse saccharification

The use of microbial enzyme cocktails for the conversion of polysaccharides of plant origin into fermentable sugars is a global trend. The objectives of this study were to optimize the production of cellulases and hemicellulases by the fungus Lichtheimia ramosa, evaluate the catalytic properties of the produced enzymes, and apply these biocatalysts in the saccharification of sugarcane bagasse. The production of carboxymethylcellulase (CMCase), β-glucosidase, xylanase, and β-xylosidase by L. ramosa were 168.1 ± 2.2, 270.4 ± 8.9, 34 ± 0.8, and 199.2 ± 2.6 U/g of dry substrate, respectively. The optimum pH for the activity of the enzymes ranged between 4.5 and 5.5, and the optimum temperature varied between 55 °C and 65 °C. The enzymes were stable within a wide range of pH, and approximately 95% of their original activity was preserved when incubated for 1 h at 55 °C. The half-lives (t1/2) of CMCase, β-glucosidase, xylanase, and β-xylosidase were 68, 59, 52, and 54 min, respectively, when incubated at 60 °C. The enzymes were stable in solutions containing ethanol (10%), and the kinetic parameters (Km and Vmax) demonstrated that β-glucosidase from L. ramosa was competitively inhibited by glucose. The enzyme extract produced by L. ramosa was used for the saccharification of sugarcane bagasse pretreated with glycerol and the highest yield of glucose (10.66%) was obtained at 24 h of hydrolysis. The characteristics of the enzymes, combined with the efficiency in hydrolyzing sugarcane bagasse, allow for the application of this enzyme extract to processes of cellulose saccharification for the production of second-generation ethanol.

Cellulases and xylanases production by endophytic fungi by solid state fermentation using lignocellulosic substrates and enzymatic saccharification of pretreated sugarcane bagasse

Endophytic fungi are widely studied as producers of secondary metabolites of biotechnological interest. In recent years, the interest in these fungi as new sources of enzymes, especially hydrolytic, has increased. In the present study, 14 strains of endophytic fungi not yet explored as enzymes sources were randomly chosen and prospected for cellulases and xylanases production by solid-state fermentation. Initially, fungi were cultivated in a mixture (1:1 w/w) of sugarcane bagasse and wheat bran for 7 days, at 28 °C. In this initial screening, 4 fungi excelled in endoglucanase activity (U/g): Cladosporium cladosporioides PAJ 03 (88.51 ± 1.0), Phomopsis stipata SC 04 (83.44 ± 7.7), Trichoderma viridae PAJ 01 (64.56 ± 4.0) and Botryosphaeria sp. AM 01 (42.79 ± 1.6). On the other hand, the following 4 fungi stood out in relation to β-glucosidase activity (U/g): Saccharicola sp. EJC 04 (51.56 ± 2.7), Paecilomyces sp. SF 021 (33.19 ± 9.2), Ustilaginoidea sp. CV 04 (29.75 ± 0.8) and Ustilaginoidea sp. XYA 04 (21.72 ± 3.05). Among these fungi, P. stipata SC 04 and Botryosphaeria sp. AM 01 were the best producers of xylanase and β-xilosidase (694,33 and 4,87 U/g, respectively). These 8 fungi were then cultured in new mixtures (1:1 w/w) of lignocellulosic substrates. Botryosphaeria sp. AM01and Saccharicola sp. EJC04 stood out regarding endoglucanase and β-glucosidase activities (184.74 ± 6.0 and 92.28 ± 9.57 U/g, respectively) when cultivated on cotton seed meal and wheat bran and were selected to continue the study. The influence of time cultivation, inoculum amount and substrate initial moisture content was evaluated and the best condition for cellulases production was 192 h, six mycelial plugs and 65%, respectively, for both fungi. Cellulases and xylanases produced under these conditions were characterized and optimum pH and temperature values were between 4.5–6 and 60–75 °C, respectively. The enzymes were stable over a wide pH range and under 30–70 °C. β-glucosidase from both isolates retained about 75–80% of their activity in the presence of glucose at 6 mM. The presence of ethanol stimulated β-glucosidase activity from Botryosphaeria sp. AM01 (about 60% higher in the presence of ethanol at 15%). On the other hand, the activity of β-glucosidase produced by Saccharicola sp. EJC 04 was reduced at ethanol concentrations above 15%. A blend of the enzymatic extracts was used to saccharify pretreated sugarcane bagasse and a face-centered central composite design was used to find the best conditions. Under the predicted optimum condition (50 °C, 5% of sugarcane bagasse, 150 U g−1 of endoglucanase and 20 h), glucose and xylose concentrations obtained were 3.56 and 1.66 mg mL−1, respectively. These results show that the 14 endophytic fungi studied have potential to be explored as producers of plant material degrading enzymes. Botryosphaeria sp. AM01 and Saccharicola sp. EJC 04 are promising in relation to the production of cellulases and xylanases and their enzymatic extracts have potential for application in pre-treated sugarcane bagasse saccharification processes.

Fed-batch strategies for saccharification of pilot-scale mild-acid and alkali pretreated sugarcane bagasse: Effects of solid loading and surfactant addition

High-solid enzymatic hydrolysis of lignocellulosic biomass is a key approach for high titer and reduced downstream costs in second generation ethanol production. Combining a pilot-scale (80 L reactor) mild acid pretreatment and an alkali pretreatment of sugarcane bagasse (SCB) with fed-batch strategies for high-solid enzymatic hydrolysis, more than 150 g/L of glucose was found in the hydrolysate. The best result of the fed-batch study (2.03 g/L/h of glucose productivity) was obtained with a total solids content of 27%w/w (being 20%w/w of solids added at 0 h), and the addition of the total amount of the non-ionic surfactant PEG 4000 and the enzymes solely at the beginning of the reaction. A semi-simultaneous saccharification and fermentation strategy of the pretreated SCB (with the yeast inoculum occurring after 12 h of a single hydrolysis stage at most proper conditions for the cellulases) resulted in 62 g/L of ethanol after 48 h, and a productivity of up to 6.6 g/L/h. The strategy here reported indicates that it is possible to achieve ethanol titers suitable for industrial distilleries avoiding mass transfer limitations that incur in operational problems during high-solid enzymatic hydrolysis.

Bioethanol from sugarcane bagasse: Focused on optimum of lignin content and reduction of enzyme addition

To investigate the effect of delignification on enzymatic saccharification and ethanol fermentation of sugarcane bagasse (SCB), NaClO, NaOH, and Na2CO3 were used to prepare SCB with different lignin contents. We found that a lignin content of approximately 11% was sufficient for enzymatic saccharification and fermentation. Based on this result, an economical delignification pretreatment method using a combination of acid and alkali (CAA) was applied. Lignin content of 11.7% was obtained after CAA pretreatment with 0.5% w/v H2SO4 at 140 °C for 10 min and 1.0% w/v NaOH at 90 °C for 60 min. Presaccharification-simultaneous saccharification and fermentation (P-SSF) of the CAA-pretreated SCB resulted in an ethanol concentration of 43.8 g/L and an ethanol yield of 81.7%, with an enzyme loading of 15 FPU/g–CAA-pretreated SCB. Enzyme activities (filter paper, carboxymethyl cellulase, and β-glucosidase activities) were determined in liquid phase during P-SSF, indicating that the residual cellulase activity could be further used. Thus, fed-batch P-SSF was carried out, and an ethanol concentration of 43.1 g/L and an ethanol yield of 80.4% were obtained with an enzyme loading of 10 FPU/g–CAA-pretreated SCB. Fed-batch P-SSF was found to be effective to reduce enzyme loading.

Molecular characterization of a first endo-acting β-1,4-xylanase of family 10 glycoside hydrolase (PsGH10A) from Pseudopedobacter saltans comb. nov.

Abstract An endo-xylanase (PsGH10A) of family 10 glycoside hydrolase from Pseudopedobacter saltans was cloned, expressed and purified. Substrate specificity analysis of PsGH10A showed activity against β-1,4-xylans. It showed maximum activity against beechwood xylan (59.7 ± 1.1 U/mg) followed by xylan (Mw. 20,000–30,000) (57.1 ± 0.7 U/mg). PsGH10A displayed maximum activity at pH 6.0 and 40 °C. The enzyme was stable in the pH range, from 6.0 to 7.5 and showed thermostability up to 40 °C. The kinetic parameters of PsGH10A using beechwood xylan determined were Km 6.2 mg/mL and Vmax 72 U/mg. The activity of PsGH10A was 29 ± 2.4% enhanced by 2 mM Mn2+ ions and inhibited by less than 50 ± 1.6% by 2 mM Zn2+, Pb2+ or Cu2+ ions. The time-dependent TLC analysis of hydrolyzed products of beechwood xylan released by PsGH10A showed the release of xylose, xylobiose and xylotetraose as end products confirming the endolytic mode of action. PsGH10A hydrolyzed products of xylan and substituted xylan indicate production of series of short-chain xylooligosaccharides and arabinoxylo-saccharides. PsGH10A also showed saccharification of AFEX pretreated poplar and sugarcane bagasse. Therefore, it can be used for various biotechnological applications such as for prebiotic xylooligosaccharides and bioethanol production from pretreated agrowaste biomass. This is the first report on β-1,4-xylanase cloned from Pseudopedobacter saltans.

Conclusive selection of optimal parameters for cellulase production by Talaromyces verruculosus IIPC 324 under SSF via saccharification of acid-pretreated sugarcane bagasse

ABSTRACTCellulase production studies were conducted with Talaromyces verruculosus IIPC 324 under solid state fermentation (SSF), and optimal parameters were conclusively selected via saccharification of acid-pretreated sugarcane bagasse. Various physicochemical parameters affecting cellulase production under SSF were optimized. Endoglucanase and cellobiase production responded differently under individual growth conditions. Maximum endoglucanase and cellobiase activity of ≥ 250 U/g and ≥ 45 U/g respectively was obtained when the strain was grown at 24°C for 4 days with an initial moisture content of 62.5% on wheat bran supplemented with 1.62% ammonium chloride. The enzyme cocktail obtained from these optimized growth conditions yielded 8.37 ± 0.75 g L−1 reducing sugar from acid-pretreated sugarcane bagasse after 72 h at 60°C and pH 4.0. With the addition of Avicel PH-101 at 5% concentration in wheat bran, the cellulase cocktail of Talaromyces verruculosus IIPC 324 released 9.17 ± 0.60 g L−1 and 7.82 ± 0.06 g L−1 of total reducing sugars and glucose respectively at 60°C (pH 4.0) after 72 h. The addition of glucose and other simple sugars did not repress the cellulase production under SSF conditions, making Talaromyces verruculosus IIPC 324 an attractive candidate for cellulase production and its application for biofuel production from lignocellulosic biomass.

Screening and optimization of pretreatments in the preparation of sugarcane bagasse feedstock for biohydrogen production and process optimization

This work evaluated the effects of individual alkaline, sodium carbonate (Na2CO3 denoted as; NaC), sodium sulfide (Na2SO3 denoted as; NaS) and combination of NaC + NaS pretreatment for the saccharification of sugarcane bagasse (SCB). The effects of different pretreatments on chemical composition and structural complexity of SCB in relation with its saccharification were investigated. For enzymatic hydrolysis of pretreated SCB we have utilized the produced crude enzymes by Streptomyces sp. MDS to make the process more cost effective. A enzyme dose of 30 filter paperase (FPU) produced a maximum reducing sugar (RS) 592 mg/g with 80.2% hydrolysis yield from NaC + NaS pretreated SCB under optimized conditions. The resulted enzymatic hydrolysates of each pretreated SCB were applied for hydrogen production using Clostridium beijerinckii KCTC1785. NaC + NaS pretreated SCB hydrolysates exhibited maximum H2 production relative to other pretreatment methods. Effects of temperature, initial pH of culture media and increasing NaC + NaS pretreated SCB enzymatic hydrolysates concentration (2.5–15 g/L) on bioH2 production were investigated. Under the optimized conditions, the cumulative H2 production, H2 production rate, and H2 yield were 1485 mL/L, 61.87 mL/L/h and 1.24 mmol H2/mol of RS (0.733 mmol H2/g of SCB), respectively. The efficient conversion of the SCB hydrolysate to H2 without detoxification proves the viability of process for cost-effective hydrogen production.

Saccharification of Sugarcane Bagasse Using an Enzymatic Extract Produced by Aspergillus fumigatus

This study investigates the efficiency of a crude enzymatic extract produced by Aspergillus fumigatus SCBM6 by solid state fermentation (SSF) in the hydrolysis of alkali pretreated sugarcane bagasse (PTB). After SSF using in ... | Find, read and cite all the research you need on Tech Science Press

Efficient pretreatment of sugarcane bagasse via dilute mixed alkali salts (K2CO3/K2SO3) soaking for enhancing its enzymatic saccharification

Abstract To decrease alkaline dosage and increase the enzymatic saccharification of sugarcane bagasse (SB), dilute mixed alkali salts soaking (0.5% K2CO3, 0.068% K2SO3) in an autoclave at 100–125 °C for 10–60 min was attempted to pretreat SB. The increased pretreatment severity at elevated temperatures resulted in the increase of delignification and enzymatic saccharification. It was found the optimum pretreatment temperature and pretreatment time were 120 °C for 40 min. Furthermore, FTIR, XRD and SEM characterized the porosity, morphology, and crystallinity changes of the pretreated SB samples. After the enzymatic in situ saccharification of 50 g/L SB in dilute K2CO3/K2SO3 (0.35% K2CO3, 0.048% K2SO3) media for 72 h, the reducing sugars and glucose could be obtained at 32.94 and 20.18 g/L, respectively. Finally, the SB-hydrolysates containing 20 g/L glucose were used for ethanol fermentation in the presence of dilute alkali salts. After 48 h, the ethanol yield was 0.394 g ethanol/g glucose, which represents 77.25% of the theoretical yield. In conclusion, an effective process about the biomass pretreatment, enzymatic saccharification and ethanol fermentation was successfully demonstrated in “one-pot” media containing low loading of alkali salts K2CO3/K2SO3.

The β-xylosidase from Ceratocystis fimbriata RM35 improves the saccharification of sugarcane bagasse

Abstract The phytopathogenic fungus Ceratocystis fimbriata produced an extracellular β-xylosidase when grown in mineral medium with wheat bran as carbon source. The enzyme was purified and characterized. The molecular mass was estimated by SDS-PAGE (161.6 kDa). The enzyme showed maximum activity at pH 3.9 and 65 °C, and it showed to be significantly thermostable at 60 °C, maintaining 70% of its maximum activity after 24 h of incubation at this temperature. The KM and VMAX using ρNρβXyl were 0.326 mM and 0.91 × 10−3 µmol/min, respectively. The β-xylosidase was partially inhibited by 1 mM of aluminum chloride, copper sulfate II, iron sulfate and SDS. The β-xylosidase combined with a xylanase had an additive effect on beechwood xylan hydrolysis, generating xylose as a final product. The supplementation of the enzymatic cocktail Multifect CL® with the β-xylosidase generated a more efficient hydrolysis of alkali-pretreated sugarcane bagasse when compared to the saccharification performed only by the cocktail Multifect CL®, showing an increase of 97.7% and 45.7% in glucose and xylose release, respectively.

Optimized feeding schemes of simultaneous saccharification and fermentation process for high lactic acid titer from sugarcane bagasse

A simultaneous saccharification and fermentation (SSF) process of pretreated sugarcane bagasse by Lactobacillus pentosus was designed and optimized for lactic acid (LA) production. Different feeding schemes in SSF process were studied for their effects on LA production efficiency. In addition to feeding optimization, adaptation of seed cultivation in hydrolysates was necessary to achieve high LA yield and productivity. LA yield and productivity was enhanced by 1.43 folds with cell feeding in comparison to initial cell addition in SSF. Likewise, pulse enzyme feeding was preferred condition for high LA production efficiency. A combinatorial feeding of pretreated bagasse, enzyme and cell enables a maximum LA titer of 72.75g/L by L. pentosus with 0.61g/g LA yield and 1.01g/L-hr LA productivity. The SSF process with optimizing feeding scheme of pretreated biomass, enzyme and cell could provide lignocellulose-based process platform for achieving high LA titer meeting techno-economic requirements.

Study of activators and inhibitors on cellulase production from isolated Trichoderma koningii for effective saccharification of sugarcane bagasse

ABSTRACTIn the present study, extracellular cellulase and xylanase production from isolated fungi Trichoderma koningii KY705013 was carried out under solid state fermentation. This study also focused on the influence of various parameters like carbon, nitrogen and divalent metal ions on the production of enzymes. Increased production of cellulase and xylanase was noticed at an optimal temperature of 35 °C and pH 6.0. Optimized media containing CMC as the carbon source and ammonium sulphate as the nitrogen source with 2 mM EDTA showed a total activity of 253.67 U, 120.15 U and 87.56 U for CMCase, FPase and xylanase, respectively. The results of the present study revealed an increase of approximately 60% in enzyme production using optimized media rather than un-optimized media.

Sugarcane bagasse saccharification by purified β-glucosidases from Chrysoporthe cubensis

A set of β-glucosidases from the phytopathogenic fungus Chrysoporthe cubensis was partially purified, characterized and evaluated for its potential application in the process of sugarcane bagasse saccharification. C. cubensis was grown in solid state fermentation (SSF) containing wheat bran as carbon source. The group of β-glucosidases, containing at least three β-glucosidases, was purified through ion exchange and gel filtration chromatography. The set of β-glucosidases exhibited maximum activity at pH 4.0 and 60 °C and showed high thermal stability at 50, 60 and 70 °C. The β-glucosidases were specific for hydrolysis of glucose residues in the β position. The km values of 0.132 and 0.7816 mM were obtained using ρNPβGlc and cellobiose as substrates, respectively. The β-glucosidases were competitively inhibited by glucose, with Ki value of 8.43 mM. Saccharification of pretreated sugarcane bagasse by a commercial enzyme cocktail supplemented with the β-glucosidases promoted efficient release of sugars. Saccharification performed by the Chrysoporthe cubensis extract supplemented with β-glucosidases promoted a higher xylose yield. The results suggest that β-glucosidases from Chrysoporthe cubensis have great potential to be used as a supplement of enzymatic preparations.

Enhanced enzymatic saccharification of sugarcane bagasse pretreated by sodium methoxide with glycerol

Sodium methoxide (CH3ONa) with glycerol pretreatment (CWGP) was performed to improve the enzymatic digestibility of sugarcane bagasse (SCB). Response surface methodology was utilized to optimize the CWGP parameters for pretreating SCB from the perspective of total fermentable sugar yield (TFSY) and total fermentable sugar concentration (TFSC). Under the optimal CWGP conditions, 0.5666g/g of TFSY (0.82% CH3ONa, 1.11h, 150°C) and 17.75g/L of TFSC (0.87% CH3ONa, 1.38h, 149.27°C) were achieved, corresponding to delignification of 79.05% and 79.34%, respectively. Compared the pretreatment using glycerol or CH3ONa alone, the CWGP has significant synergies to enhance the enzymatic efficiency of SCB. The physical and chemical characteristics of untreated and pretreated SCBs were analyzed using FT-IR, XRD, and SEM, and the results suggest that CWGP significantly increased the susceptibility of the substrates to enzymatic digestibility. Ultimately, CWGP might be a prospective candidate for the pretreatment process of enzyme-based lignocellulosic biorefineries.

Enzymatic in situ saccharification of sugarcane bagasse pretreated with low loading of alkalic salts Na2SO3/Na3PO4 by autoclaving

Sugarcane bagasse (SCB) is an abundant, renewable and inexpensive agricultural byproduct for the production of biofuel and other biobased products. To effectively saccharify SCB with cellulases, combination with dilute alkali salts Na2SO3/Na3PO4 (0.4% Na3PO4, 0.03% Na2SO3) at 7.5% sulfidity and hot water (DASHW) in “one-pot” pretreatment media by autoclaving at 110°C for 40min was attempted to pretreat SCB in this study. Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated Na2SO3/Na3PO4-SCB solid residue, which indicated that combination pretreatment could effectively remove lignin and hemicellulose for enhancing enzymatic saccharification. After 72h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50g/L Na2SO3/Na3PO4-SCB in dilute Na2SO3/Na3PO4 (0.27% Na3PO4, 0.02% Na2SO3) media were obtained at 33.8 and 21.8g/L, respectively. Finally, the SCB-hydrolysates containing 20g/L glucose were used for ethanol fermentation in the presence of dilute alkali salts. After 48h, the ethanol yield was 0.42g ethanol/g glucose, which represents 82.1% of the theoretical yield. In conclusion, this study provided an effective pretreatment strategy for enhancing SCB’s saccharification, which has potential application of other lignocellulosic materials.

One-vessel saccharification and fermentation of pretreated sugarcane bagasse using a helical impeller bioreactor

The effect of Tween® 80 and the cellulase load, on the enzymatic hydrolysis of hydrothermally pretreated sugarcane bagasse (HPSB), was evaluated in shake flask experiments, using experimental design. The optimized conditions were further applied in a second set of shake flask experiments to study the effect of the biomass load. The overall optimum parameters, e.g., 6.9% Tween® 80, 15 FPU/g glucan, and 150 g/L (dry HPSB), were used in hydrolysis experiments carried out in a laboratory-scale bioreactor equipped with a helical impeller. After a 48 h reaction time, 60% of the HPSB glucan content was hydrolyzed into glucose. The same bioreactor and hydrolysis conditions were used for one-vessel saccharification and fermentation experiments as follows: 150 g/L (dry HPSB) was hydrolyzed at 50 °C and 150 rpm for either 24 or 48 h, followed by the bioreactor’s temperature and mixing decrease to 30 °C and 90 rpm for ethanol fermentation by Saccharomyces cerevisiae. Experiments resulted in ethanol yields of 48 or 52%, for hydrolysis time of 24 or 48 h, respectively, taking into account the HPSB glucan content. The best ethanol productivity, for the overall process of 0.51 g/L.h, was achieved for the 24 h hydrolysis time.

Optimal Design of Cost-Effective Simultaneous Saccharification and Co-fermentation Through Integrated Process Optimization

This study presents an integrative design of experiment (intDoE) methodology for process optimization using a combination of experimental design, process flowsheet simulation, and economic model. This multilayered framework was implemented to simulate and optimize a simultaneous saccharification and co-fermentation (SSF) process of sugarcane bagasse to ethanol for improving process economic efficiency. Using intDoE based on product titer and economic profit criteria, the SSF process was designed for operation at optimal xylanase/cellulases enzymes, optimal Scheffersomyces stipitis/Saccharomyces cerevisiae yeast cells, and optimal oxygen supply to maximize ethanol titer and to minimize ethanol selling price. The optimal SSF process achieved an ethanol titer of 81.5 g/L, equivalent to the minimal ethanol selling price of 1.4 USD/gal. The results proved the efficiency of intDoE approach that permitted the design and optimizing of fully integrated processes which was not considered by the traditional design of experiment methods. Hence, this novel intDoE optimization tool is useful for bioprocess design in which the integrated process simulation can be performed to select the optimal operating conditions for maximized production efficiency and process economy.