Fed-batch Simultaneous Saccharification And Fermentation Research Articles

Integrating use of sugarcane bagasse with sugarcane juice for efficient l-lactic acid production through fed-batch simultaneous saccharification and fermentation: Process configurations and kinetic analysis

The present study investigated the utilization of sugarcane juice (SJ) and sugarcane bagasse (SB) for L-lactic acid (L-LA) production by a newly isolated Enterococcus gallinarum TSKKU D-6. SJ was first investigated as a single substrate, yielding 43.9 ± 2.9 g-LA/L, with a fermentation efficiency of 72.0 ± 0.1 %, based on sucrose content in SJ. On the other hand, simultaneous saccharification and fermentation (SSF) of SB as a single substrate yielded 68.2 ± 2.7 g-LA/L, with a fermentation efficiency of 74.1 ± 0.0 %, based on cellulose content in SB. SSF of SJ and SB as co-substrates was subsequently carried out to increase the acid production, where SJ was first fermented, followed by the addition of SB to enhance LA titer. Effects of mixing and SB addition strategy on the kinetics and economic feasibility of L-LA production were investigated using a bioreactor equipped with a single and dual impellers, as well as the use of dual impellers under fed-batch SSF. The use of single and dual impellers gave similar L-LA titers of 95.9 ± 1.4 and 102.6 ± 0.6 g/L, respectively. Nevertheless, the use of dual impellers shortened the processing time, enhancing LA productivity from 0.37 to 1.12 g/(L·h). As a result, the economic yield and productivity were improved by 7.1 % and 187.5 %, respectively. Better still, performing fed-batch SSF with the use of dual impellers further improved the economic productivity by 8.7 %. This study demonstrated that integrating use of SB as a low-cost substrate considerably enhanced the acid production and lessened the use of SJ. It was also demonstrated that mixing, and process configuration are critical factors determining the process performance.

Biovalorizing felled oil palm trunk as a sole feedstock for lactic acid production through efficient simultaneous saccharification and fermentation

This study aimed to develop practical biorefinery process for bio-valorizing felled oil palm trunk (OPT) as a sole feedstock for lactic acid (LA) production. OPT was separated into oil palm sap (OPS), vascular bundle (OPT-VB), and parenchyma (OPT-PA) fractions. OPS containing high amounts of sugars (38.69 g/L) and nitrogen (0.63 g/L), could be used directly for LA production by Lactobacillus acidophilus and also as base medium for simultaneous saccharification and fermentation (SSF) of OTP-VB and OPT-PA. The repeated SSF efficiently utilized cellulosic OPT-VB and produced LA up to 50–71 g/L during five cycles. Due to high water-absorbing and swelling properties of OPT-PA, it could not be initially added at high loadings. It was then intermittently added through fed-batch SSF, which effectively produced LA of 72.85 ± 1.61 g/L. These strategies have shown the efficient biorefinery process for biovalorization of OPT and may also be applicable to other similar agricultural wastes.

Techno-economical valorization of sugarcane bagasse for efficiently producing optically pure D-(−)-lactate approaching the theoretical maximum yield in low-cost salt medium by metabolically engineered Klebsiella oxytoca

Sugarcane bagasse (SCB) was utilized for efficiently producing optically pure D-(−)-lactate by Klebsiella oxytoca KIS004-91T strain. Cellulase (15 U/g NaOH-treated SCB) sufficiently liberated high sugars with saccharifications of 79.8 % cellulose and 52.5 % hemicellulose. For separated hydrolysis and fermentation, D-(−)-lactate was produced at 53.5 ± 2.1 g/L (0.98 ± 0.01 g/g sugar utilized or 0.71 ± 0.01 g/g total sugars) while D-(−)-lactate at 47.2 ± 1.8 g/L (0.78 ± 0.03 g/g sugar used or 0.69 ± 0.01 g/g total sugars) was obtained under simultaneous saccharification and fermentation (SSF). D-(−)-lactate at 99.9 ± 0.9 g/L (0.97 ± 0.01 g/g sugar utilized or 0.78 ± 0.01 g/g total sugars) was improved via fed-batch SSF. Based on mass balance, raw SCB of 7 kg is required to produce 1 kg D-(−)-lactate. Unlike others, D-(−)-lactate production was performed in low-cost salt medium without requirements of rich nutrients. Costs regarding medium, purification, and waste disposal may be reduced. This unlocks economic capability of SCB bioconversion or agricultural and agro-industrial wastes into high valuable D-(−)-lactate.

Fed-batch SSF with pre-saccharification as a strategy to reduce enzyme dosage in cellulosic ethanol production

The pulp and paper industry is a strategic sector to be converted into a forest-based biorefinery, taking advantage of know-how, existing infrastructures and well-established logistic operations to deal with a daily high volume of forest residues. Bioethanol production from Eucalyptus globulus bark previously pretreated by kraft pulping was assessed following two configurations at the bioreactor scale: separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). This last configuration was optimized by using a pre-saccharification and a fed-batch feeding (FB PS-SSF), allowing for a reduction in the enzyme dosage from 25 to 10 FPU gCH−1, which is very advantageous from an economic point of view. For 10 FPU gCH−1 enzyme dosage and 20 % (w/v) total solids loading, an ethanol concentration of around 70.6 g L−1 was accomplished, corresponding to overall conversion efficiency and productivity of about 78 % and 1.35 g L−1 h−1, respectively. Increasing solids loading from 20 to 26 % (w/v), using the same enzyme dosage, resulted in the highest ethanol concentration (84.6 g L−1) despite the too-long assay and the decline in productivity. Overall, FB PS-SSF improved bioethanol concentration and allowed decreased enzymatic usage over SHF, maintaining high ethanol concentration.

Simultaneous saccharification and butanediol production from unpretreated lignocellulosic biomass using an enzymatic cocktail of a newly constructed bacterial consortium

Bioconversion lignocellulosic biomass (LCB) to 2,3-butanediol (2,3-BDO) is a sustainable and energy-intensive practice, but its economic feasibility has been hindered by costly pretreatment and the cumbersome fermentation process. Herein, the hindgut metagenome of Cyrtotrachelus buqueti is assembled and sequenced to construct bacterial consortia for efficient LCB degradation. One of these consortia, named artificial synthetic bacteria community II (ASCII), is effective in degrading unpretreated LCB, achieving degradation rates of 85.33% for cellulose, 77.43% for hemicellulose, and 57.63% for lignin. The secretory protein extracted from ASCII is used for simultaneous saccharification and fermentation (SSF) from unpretreated LCB. Furthermore, fed-batch SSF resulted in 40.62 g/L of 2,3-BDO with a productivity of 0.42 g/L/h reached by Klebsiella sp. CQHG35. This study provides a new approach for the construction of bacterial consortia and their use in SSF for the production of 2,3-BDO from unpretreated LCB, representing a significant breakthrough in this field.

Comparison of marine and rushton impeller in high solid loading of two-step pretreated oil palm trunk using simultaneous saccharification and fermentation for ethanol production

Substrate loading enhancement in fermenter generates difficulty in mixing that results in low ethanol yield owing to insufficient mass transfer. Thus, this study evaluated the efficiency of a six-blade Rushton turbine and a three-blade marine type propeller in a 3 L stirred tank bioreactor (STBR) by using steam exploded and alkaline pretreated oil palm trunk (OPT) fibers in a unique batch and fed-batch strategy. The fed-batch began with 5% (w/v) solid loading and after 12 h of simultaneous saccharification and fermentation (SSF) reaction, 2.5% (w/v) solid was added in the bioreactor with 6 h interval. The marine and Rushton impellers were compared at 5% (w/v) batch and 20% (w/v) fed-batch SSF, using agitation rate of 100 rpm. At 5% (w/v) solid loading, the highest ethanol concentration and theoretical yield were 15.66 ± 1.71 g/L and 61.69 ± 2.34%, and 12.10 ± 0.98 g/L and 54.01 ± 3.52%, respectively for marine and Rushton impeller. At high solid loading (20% w/v), the marine impeller achieved maximum ethanol concentration of 41.33 ± 2.02 g/L at 72 h of fermentation, with a low power consumption of 54.73 kW. The Rushton impeller resulted in ethanol concentration of 39.08 ± 1.47 g/L at 96 h of fermentation with relatively higher power consumption of 83.62 kW. The marine impeller is therefore efficient with the fed-batch strategy.

Enhanced cellulosic ethanol production via fed-batch simultaneous saccharification and fermentation of sequential dilute acid-alkali pretreated sugarcane bagasse

This study reports high gravity fed-batch simultaneous saccharification and fermentation (FB-SSF) of sequentially pretreated sugarcane bagasse (SCB) for enhanced bioethanol by employing multiple inhibitor tolerant Kluyveromyces marxianusJKH5 C60. FB-SSF with intermittent feeding of SCB (total 20 % solid loading) and enzyme (total dose of 20 FPU/g) at 6 and 12 h resulted in superior bioethanol production at42 °C. Under optimizedlab-scaleFB-SSF, the maximum ethanoltiter, efficiency and productivities were73.4 ± 1.2 g/L,78 % and 3.0 g/L/h, respectively, after 72 h in presence of inhibitors (acetic acid, furfural, and vanillin at 3, 1, and 1 g/L, respectively). Furthermore, pentose rich dilute acid hydrolysate of SCB was subjected to fermentation by Pichia stipitis NCIM 3499, resulting in ethanol titer of 6.8 g/L. Overall ethanol yield during the developed process was 260.1 g/kg native SCB, which proves industrial potential of the developed bioethanol conversion process.

Cleaner 2,3-butanediol production from unpretreated lignocellulosic biomass by a newly isolated Klebsiella pneumoniae PX14

Bioconversion lignocellulosic biomass (LCB) to 2,3-butanediol (2,3-BDO) is a sustainable and energy-intensive practice, but its economic feasibility has been hindered by costly pretreatment and the cumbersome fermentation process. Herein, a lignocellulolytic strain Klebsiella pneumoniae PX14 is isolated from insect gut, showing effective degradation on unpretreated LCB with rates of 51.48 % for cellulose, 62.13 % for hemicellulose, and 41.42 % for lignin, while with a low 2,3-BDO titer of 3.26 g/L. Consequently, the secretory proteins of PX14 cultured on the bamboo biomass-containing medium are extracted for the construction of an enzyme cocktail with commercial cellulase. The designed enzyme cocktail achieves efficient saccharification of the unpretreated LCB, resulting in 42.90 g/L reducing sugars released, which is significantly higher than that from the secretory protein or cellulase only. These high sugars titer is also effective conversion to 2,3-BDO of 19.11 g/L titer by PX14 after further optimization. For the first time, the enzyme cocktail is tried for application in simultaneous saccharification and fermentation (SSF) of 2,3-BDO from unpretreated LCB. This fed-batch SSF resulted in 47.46 g/L of 2,3-BDO with 0.36 g/L/h productivity under high solid loading of 20 % due to the high substrate concentration tolerance of PX14. Finally, whole-genome sequencing reveals the robustness of K. pneumoniae PX14 and its molecular mechanism for such a process. These results provide a robustness strain of K. pneumoniae PX14 and its novel application in SSF of 2,3-BDO from unpretreated LCB, showing a great breakthrough in this process.

Strategies for Improvement of Lipid Production by Yeast Trichosporon oleaginosus from Lignocellulosic Biomass.

Microbial lipids have similar fatty acid composition to plant oils, and therefore, are considered as an alternative feedstock for biodiesel production. Oleaginous yeasts accumulate considerable amounts of lipids intracellularly during growth on low-cost renewable feedstocks such as lignocellulosic biomass. In this study, we cultivated yeast Trichosporon oleaginosus on hydrolysate of alkaline pretreated corn cobs. Different process configurations were evaluated and compared, including separate hydrolysis and fermentation (SHF) with cellulase recycle and simultaneous saccharification and fermentation (SSF) in batch and fed-batch mode. At low enzyme loading, the highest lipid concentration of 26.74 g L−1 was reached in fed-batch SSF fed with 2.5% (g g−1) substrate. Batch SHF was conducted for four rounds with recycling the cellulase adsorbed on unhydrolyzed lignocellulosic biomass. Thirty percent of cellulase saving was achieved for rounds 2–4 without compromising productivity and lipid yield. The addition of Tween 80 to lignocellulosic slurry improved the hydrolysis rate of structural carbohydrates in pretreated lignocellulosic biomass. Furthermore, supplementing the growth medium with Tween 80 improved lipid yield and productivity without affecting yeast growth. Oleaginous yeast T. oleaginosus is a promising strain for the sustainable and efficient production of lipids from renewable lignocellulosic feedstock.

Cellulase Addition and Pre-hydrolysis Effect of High Solid Fed-Batch Simultaneous Saccharification and Ethanol Fermentation from a Combined Pretreated Oil Palm Trunk.

In the current study, alkaline hydrogen peroxide pretreated oil palm trunk fibers were subjected to ethanol production via simultaneous saccharification and fermentation (SSF). The effect of high substrate loading, enzyme and substrate feeding strategy, and influence of a pre-hydrolysis step in SSF was studied to scale up ethanol production. In the enzyme feeding strategy, the addition of an enzyme at the start of fed-batch SSF significantly (p < 0.05) increased ethanol concentration to 51.05 g/L, ethanol productivity (QP) to 0.61 g/L·h, and ethanol yield (YP/S) to 0.31 g/g, with a theoretical ethanol yield of 60.65%. Furthermore, the initial velocity of the enzyme (V0) in the first 8 h was 2.27 (g/h) with a glucose concentration of 18.17 g/L. On the other hand, the substrate feeding strategy and pre-hydrolysis simultaneous saccharification and fermentation (PSSF) process were studied in a 1 L fermenter. PSSF in fed batch with 10 and 20% (w/v) significantly improved enzyme hydrolysis, circumvent the problems of high viscosity, reduced overall fermentation time, and gave the highest ethanol concentration of 51.66 g/L, ethanol productivity (QP) of 0.72 g/L·h, ethanol yield (YP/S) of 0.31 g/g, and theoretical ethanol yield of 60.66%. In addition, PSSF with 10 and 20% significantly increased the initial velocity of the enzyme (V0) to 4.64 and 4.40 (g/h) and glucose concentration to 37.14 and 35.27 g/L, respectively. This result indicated that ethanol production by PSSF along with substrate feeding could enhance ethanol production efficiently.

Bioethanol Production from Cellulose-Rich Corncob Residue by the Thermotolerant Saccharomyces cerevisiae TC-5.

This study aimed to select thermotolerant yeast for bioethanol production from cellulose-rich corncob (CRC) residue. An effective yeast strain was identified as Saccharomyces cerevisiae TC-5. Bioethanol production from CRC residue via separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), and prehydrolysis-SSF (pre-SSF) using this strain were examined at 35–42 °C compared with the use of commercial S. cerevisiae. Temperatures up to 40 °C did not affect ethanol production by TC-5. The ethanol concentration obtained via the commercial S. cerevisiae decreased with increasing temperatures. The highest bioethanol concentrations obtained via SHF, SSF, and pre-SSF at 35–40 °C of strain TC-5 were not significantly different (20.13–21.64 g/L). The SSF process, with the highest ethanol productivity (0.291 g/L/h), was chosen to study the effect of solid loading at 40 °C. A CRC level of 12.5% (w/v) via fed-batch SSF resulted in the highest ethanol concentrations of 38.23 g/L. Thereafter, bioethanol production via fed-batch SSF with 12.5% (w/v) CRC was performed in 5-L bioreactor. The maximum ethanol concentration and ethanol productivity values were 31.96 g/L and 0.222 g/L/h, respectively. The thermotolerant S. cerevisiae TC-5 is promising yeast for bioethanol production under elevated temperatures via SSF and the use of second-generation substrates.

Poly-γ-glutamic acid production by simultaneous saccharification and fermentation using corn straw and its fertilizer synergistic effect evaluation.

Agricultural wastes rich in lignocellulosic biomass have been used in the production of poly-γ-glutamic acid (γ-PGA) through separate hydrolysis and fermentation (SHF), but this process is complicated and generates a lot of wastes. In order to find a simpler and greener way to produce γ-PGA using agricultural wastes, this study attempted to establish simultaneous saccharification and fermentation (SSF) with citric acid-pretreated corn straw. The possibility of Bacillus amyloliquefaciens JX-6 using corn straw as substrate to synthesize γ-PGA was validated, and the results showed that increasing the proportion of glucose in the substrate could improve the γ-PGA yield. Based on these preliminary results, the corn straw was pretreated using citric acid. Then, the liquid fraction (xylan-rich) was used for cultivation of seed culture, and the solid fraction (glucan-rich) was used as the substrate for SSF. In a 10-L fermenter, the maximum cumulative γ-PGA concentration in batch and fed-batch SSF were 5.08 ± 0.78g/L and 10.78 ± 0.32g/L, respectively. Moreover, the product from SSF without γ-PGA extraction was used as a fertilizer synergist, increasing the yield of pepper by 13.46% (P < 0.05). Our study greatly simplified the production steps of γ-PGA, and each step achieved zero emission as far as possible. The SSF process for γ-PGA production provided a simple and green way for lignocellulose biorefinery and sustainable cultivation in agriculture.

Pilot scale demonstration of a two-stage pretreatment and bioethanol fermentation process for cotton gin trash

A two-stage dilute acid and steam explosion (SE) pretreatment process was developed and evaluated at pilot scale for ethanol production from cotton gin trash (CGT). Optimal conditions for CGT processing were defined as 1:6 solids to liquids ratio with 9% H2SO4 wt. on solids at 180 °C for 15 min. during stage 1 with ensuing pressed fibres successively exposed to SE at 200 °C for 5 min during stage 2. SE fibres were highly acquiescent to enzyme hydrolysis (76%) in the presence of PEG 6000, yielding 381 g glucose kg−1 fibre. Simultaneous saccharification and fermentation (SSF) trials validated the selected process option and additional fed-batch SSFs confirmed titres above the minimum 4% ww-1 benchmark for economically viable distillation. The practicality of converting CGT to ethanol was demonstrated at pilot scale with titres above 4% ww-1 and a conversion efficiency of 60% t−1 dry GCT.

Boosting second-generation ethanol titers from green coconut fiber by using high-concentration polyethylene glycol

Efforts have been made to improve and modify lignocellulosic pretreatments, but this step corresponds to a high cost in second-generation ethanol production. Previous studies have shown that high-concentration polyethylene glycol (PEG) is a possible way to dispense chemical and physicochemical pretreatments and increase ethanol production from lignocellulosic material. However, no operational conditions of this strategy were optimized. The present study investigated the effects of operational conditions on simultaneous saccharification and fermentation (SSF) performance using high PEG concentrations and green coconut fiber (GCF) as a substrate. The high-concentration PEG (150 g.L−1) increased ethanol production compared to the PEG-free, 10, and 50 g.L−1 PEG conditions. Using 20 % (w.v−1) solid loading, the batch SSF cultivation with PEG 1500 and without supplementary nutrients reached ethanol production and ethanol yield equal to 22.21 g.L−1 and 64.0 %, respectively. The batch SSF cultivation with 30 % (w.v−1) solid loading presented mass transfer limitations. The addition of salts, yeast extract, or peptone improved ethanol production. Inhibition by ethanol on the Saccharomyces cerevisiae CAT-1 strain was indifferent to the presence of PEG 1500, while the addition of PEG ensured the cellulolytic activity reuse after three fermentation cycles. The fed-batch SSF with PEG facilitated the GCF liquefaction so that it was possible to operate with up to 30 % (w.v−1) solid loading without problems of viscosity and free water. Using 150 g.L−1 PEG 1500 and enzyme loading equal to 13.3 filter paper unit. g−1, the fed-batch SSF reached 35.1 g.L−1 ethanol at 48 h, representing an increase of 70 % compared to the fed-batch SSF without PEG.

Bioconversion of wastewater-derived duckweed to lactic acid through fed-batch fermentation at high-biomass loading

After being collected from the wastewater treatment system, duckweed biomass which is rich in starch and protein has the potential to be converted to valuable chemicals. This study aimed to establish a fermentation process for bioconversion of duckweed biomass derived from wastewater treatment to lactic acid (LA) by Lactobacillus casei. The Lactobacillus casei CICC 23184 showed the best LA production ability in duckweed-based medium among five strains. Simultaneous saccharification and fermentation (SSF) and separated hydrolysis and fermentation (SHF) were conducted, and the SSF had better performance even with lower enzyme dosage. No extra nitrogen source needed supplying into duckweed-based media. In batch fermentation, biomass loading of 220 g kg−1 was optimal with LA concentration of 72.51 ± 2.81 g kg−1 and yield of 0.35 ± 0.01 g g−1dry biomass. The highest LA concentration (100.36 ± 3.31 g kg−1), yield (0.38 ± 0.01 g g−1dry biomass), and productivity (2.09 ± 0.07 g kg−1 h−1) were obtained through fed-batch SSF at a final biomass loading of 260 g kg−1. This study demonstrated that it is feasible to utilize duckweed biomass as feedstock to produce LA through fermentation, and a fed-batch SSF at high-biomass loading was successfully established. This study provides a novel strategy for sustainable recycling of duckweed biomass derived from wastewater treatment.

High-Titer Lactic Acid Production by Pediococcus acidilactici PA204 from Corn Stover through Fed-Batch Simultaneous Saccharification and Fermentation.

Lignocellulose comprised of cellulose and hemicellulose is one of the most abundant renewable feedstocks. Lactic acid bacteria have the ability to ferment sugar derived from lignocellulose. In this study, Pediococcus acidilactici PA204 is a lactic acid bacterium with a high tolerance of temperature and high-efficiency utilization of xylose. We developed a fed-batch simultaneous saccharification and fermentation (SSF) process at 37 °C (pH 6.0) using the 30 FPU (filter paper units)/g cellulase and 20 g/L corn steep powder in a 5 L bioreactor to produce lactic acid (LA). The titer, yield, and productivity of LA produced from 12% (w/w) NaOH-pretreated and washed stover were 92.01 g/L, 0.77 g/g stover, and 1.28 g/L/h, respectively, and those from 15% NaOH-pretreated and washed stover were 104.11 g/L, 0.69 g/g stover, and 1.24 g/L/h, respectively. This study develops a feasible fed-batch SSF process for LA production from corn stover and provides a promising candidate strain for high-titer and -yield lignocellulose-derived LA production.

Consolidated bioprocesses for efficient bioconversion of palm biomass wastes into biodiesel feedstocks by oleaginous fungi and yeasts

Consolidated bioprocesses for bioconversion of lignocellulosic biomass into biodiesel feedstocks were developed. Palm empty fruit bunch (EFB) was biologically pretreated coupling with fungal lipid production (121.4 ± 2.7 mg/g-EFB) by lignocellulolytic oleaginous fungi prior to lipid production by oleaginous yeasts. In subsequent separate hydrolysis and fermentation (SHF) of fungal pretreated EFB (FPEFB), the oleaginous yeast with the maximum lipid yield of 37.0 ± 0.1 mg/g-FPEFB was screened. While a higher lipid yield of 47.9 ± 1.5 mg/g-FPEFB was achieved in simultaneous saccharification and fermentation (SSF) with less enzyme requirement. Fed-batch SSF of non-sterile FPEFB was proven as a practical and efficient strategy to increase lipid yield up to 53.4 ± 0.5 mg/g-FPEFB. Total lipid yield by both fungi and yeast was 165.0 ± 4.4 mg/g-EFB. Interestingly, the consolidated bioprocesses of enzyme and lipid production also achieved comparable total lipid yield of 149.3 ± 6.6 mg/g-EFB. These strategies may contribute greatly to cost-effective and sustainable bioconversion of lignocellulosic biomass into biodiesel feedstocks.

Improvement in Ethanol Yield from Lignocellulo-Starch Biomass using Saccharomyces cerevisiae alone or its Co-culture with Scheffersomyces stipitis

Background:Literature on ethanol production from Lignocellulo-Starch Biomass (LCSB) containing starch besides cellulose and hemicellulose, is scanty. Fed-Batch Separate Hydrolysis And Fermentation (F-SHF) was earlier found more beneficial than Fed-Batch Simultaneous Saccharification and Fermentation (F-SSF).Objective:The study aimed at modification of the saccharification and fermentation strategies by including a prehydrolysis step prior to the SSF and compared the ethanol yields with co-culture fermentation using hexose-fermenting Saccharomyces cerevisiae and pentose-fermenting Scheffersomyces stipitis.Methods:Fed-batch hybrid-SSF and Fed-Batch Separate Hydrolysis and Co-culture Fermentation (F-SHCF) in improving ethanol yield from Steam (ST) or Dilute Sulfuric Acid (DSA) pretreated LCSBs (peels of root and vegetable crops) were studied.Results:There was a progressive build-up of ethanol during F-HSSF up to 72h and further production up to 120h was negligible, with no difference among pretreatments. Despite very high ethanol production in the initial 24h of fermentation by S.cerevisiae under F-SHCF, the further increase was negligible. A rapid hike in ethanol production was observed when S. stipitis was also supplemented because of xylose conversion to ethanol.Conclusion:While ST gave higher ethanol (296-323 ml/kg) than DSA under F-HSSF, the latter was advantageous under F-SHCF for certain residues. Prehydrolysis (24h; 50°C) enhanced initial sugar levels favouring fast fermentation and subsequent saccharification and fermentation occurred concurrently at 37°C for 120h, thus leading to energy saving and hence F-HSSF was advantageous. Owing to the low hemicellulose content in LCSBs, the relative advantage of co-culture fermentation over monoculture fermentation was not significant.

Different design configurations of simultaneous saccharification and fermentation to enhance ethanol production from cashew apple bagasse pretreated with alkaline hydrogen peroxide applying the biorefinery concept

Different strategies for simultaneous saccharification and fermentation (SSF) process were developed to enhance the productivity of ethanol by Kluyveromyces marxianus ATCC36907 as a part of biorefinery concept using cashew apple bagasse (CAB) as biomass. CAB was pretreated with 4.3% (v/v) alkaline hydrogen peroxide at pH 11.5 (CAB-AHP). Batch SSF conducted at 45 °C using 10% (w/v) CAB-AHP reported the highest concentration and ethanol yield. In the fed-batch SSF, the highest production (7.91 g ethanol/100gCAB) and ethanol yield (84.69%) were achieved using 10% (w/v) CAB-AHP initial solids load, 4% solid feeding at 24 h, and the feeding of enzymes only in the beginning of the process. The recycling of pretreatment inputs decreased 50% of the batch-SSF efficiencies, saving the consumption of water, H2O2, and NaOH in 66.67%, 48.44%, and 66.67%, respectively. Lignin was extracted from the hydrolysate with yield of 39.2%. Thus, the proposed biorefinery concept utilizes CAB to produce ethanol with high efficiency by fed-batch SSF, pretreatment input recycling, and the utilization of the extracted lignin for future applications.

L-lactic acid production by simultaneous saccharification and fermentation of dilute ethylediamine pre-treated rice straw

To effectively produce second-generation L-lactic acid (L-LA), for the first time, rice straw (RS) was pretreated by dilute ethylenediamine (EDA) and followed by fed-batch simultaneous saccharification and fermentation (SSF) under non-sterilized conditions. Specifically, the impact of pretreatment parameters included EDA concentration and pretreatment temperature on sugars and L-LA productions were evaluated. Results indicated that after pretreatment in 6% (w/v) EDA at 200 °C for 1 h and following the enzymatic hydrolysis, 42.25 g L−1 of total monomer sugars was generated. By batch SSF, the maximized 63.5 ± 3.0 g L−1and 296.8 g Kg−1 of L-LA can be obtained from the raw RS using Bacillus coagulans LA-15-2. Fed-batch SSF was further conducted and L-LA concentration of 92.5 g L−1 was obtained in the final fermentation broth. Correspondingly, L-LA productivity and yield reached 2.01 g L−1 h−1 and 578.1 g Kg−1of the pretreated RS, respectively. This study provided a novel environmental-friendly method for L-LA production, which successfully avoided the usage of large amount of inorganic alkali in lignocellulose pretreatment stage.