Optimization of xylitol production from xylose by a novel arabitol limited co-producing Barnettozyma populi NRRL Y-12728.

Xylitol is a widely marketed sweetener with good functionality and health-promoting properties. It can be synthetized by many yeast species in a one-step reduction of xylose. Arabinose is a common contaminant found in xylose and there is ongoing interest in finding biocatalysts that selectively produce xyltiol. From a screen of 99 yeasts, Barnettozyma populi Y-12728 was found to selectively produce xylitol from both mixed sugars and corn stover hemicellulosic hydrolysate. Here, fermentation conditions for xylitol production from xylose by B. populi were optimized. The medium for xylitol production was optimized through response surface methodology. The yeast produced 31.2 ± 0.4 g xylitol from xylose (50 g L-1) in 62 h using the optimized medium. The optimal pH for xylitol production was 6.0. Glucose (10 g L-1), acetic acid (6.0 g L-1), HMF (4 mM) and ethanol (2.0 g L-1) inhibited the xylitol production. The glucose inhibition was entirely mitigated by using a 2-stage aeration strategy, indicating that the yeast was inhibited by ethanol produced from glucose under low aeration. This culture strategy will greatly benefit xylitol production from hemicellulosic hydrolysates, which often contain glucose. This is the first report on optimization of xylitol production by a Barnettozyma species.

Emerging biotechnologies for production of itaconic acid and its applications as a platform chemical.

Recently, itaconic acid (IA), an unsaturated C5-dicarboxylic acid, has attracted much attention as a biobased building block chemical. It is produced industrially (>80 g L-1) from glucose by fermentation with Aspergillus terreus. The titer is low compared with citric acid production (>200 g L-1). This review summarizes the latest progress on enhancing the yield and productivity of IA production. IA biosynthesis involves the decarboxylation of the TCA cycle intermediate cis-aconitate through the action of cis-aconitate decarboxylase (CAD) enzyme encoded by the CadA gene in A. terreus. A number of recombinant microorganisms have been developed in an effort to overproduce it. IA is used as a monomer for production of superabsorbent polymer, resins, plastics, paints, and synthetic fibers. Its applications as a platform chemical are highlighted. It has a strong potential to replace petroleum-based methylacrylic acid in industry which will create a huge market for IA.

Irradiation of Yarrowia lipolytica NRRL YB-567 creating novel strains with enhanced ammonia and oil production on protein and carbohydrate substrates.

Increased interest in sustainable production of renewable diesel and other valuable bioproducts is redoubling efforts to improve economic feasibility of microbial-based oil production. Yarrowia lipolytica is capable of employing a wide variety of substrates to produce oil and valuable co-products. We irradiated Y. lipolytica NRRL YB-567 with UV-C to enhance ammonia (for fertilizer) and lipid (for biodiesel) production on low-cost protein and carbohydrate substrates. The resulting strains were screened for ammonia and oil production using color intensity of indicators on plate assays. Seven mutant strains were selected (based on ammonia assay) and further evaluated for growth rate, ammonia and oil production, soluble protein content, and morphology when grown on liver infusion medium (without sugars), and for growth on various substrates. Strains were identified among these mutants that had a faster doubling time, produced higher maximum ammonia levels (enzyme assay) and more oil (Sudan Black assay), and had higher maximum soluble protein levels (Bradford assay) than wild type. When grown on plates with substrates of interest, all mutant strains showed similar results aerobically to wild-type strain. The mutant strain with the highest oil production and the fastest doubling time was evaluated on coffee waste medium. On this medium, the strain produced 0.12 g/L ammonia and 0.20 g/L 2-phenylethanol, a valuable fragrance/flavoring, in addition to acylglycerols (oil) containing predominantly C16 and C18 residues. These mutant strains will be investigated further for potential application in commercial biodiesel production.

Hydrothermal pretreatment of sugarcane bagasse using response surface methodology improves digestibility and ethanol production by SSF.

Sugarcane bagasse was characterized as a feedstock for the production of ethanol using hydrothermal pretreatment. Reaction temperature and time were varied between 160 and 200°C and 5-20 min, respectively, using a response surface experimental design. The liquid fraction was analyzed for soluble carbohydrates and furan aldehydes. The solid fraction was analyzed for structural carbohydrates and Klason lignin. Pretreatment conditions were evaluated based on enzymatic extraction of glucose and xylose and conversion to ethanol using a simultaneous saccharification and fermentation scheme. SSF experiments were conducted with the washed pretreated biomass. The severity of the pretreatment should be sufficient to drive enzymatic digestion and ethanol yields, however, sugars losses and especially sugar conversion into furans needs to be minimized. As expected, furfural production increased with pretreatment severity and specifically xylose release. However, provided that the severity was kept below a general severity factor of 4.0, production of furfural was below an inhibitory concentration and carbohydrate contents were preserved in the pretreated whole hydrolysate. There were significant interactions between time and temperature for all the responses except cellulose digestion. The models were highly predictive for cellulose digestibility (R (2) = 0.8861) and for ethanol production (R (2) = 0.9581), but less so for xylose extraction. Both cellulose digestion and ethanol production increased with severity, however, high levels of furfural generated under more severe pretreatment conditions favor lower severity pretreatments. The optimal pretreatment condition that gave the highest conversion yield of ethanol, while minimizing furfural production, was judged to be 190°C and 17.2 min. The whole hydrolysate was also converted to ethanol using SSF. To reduce the concentration of inhibitors, the liquid fraction was conditioned prior to fermentation by removing inhibitory chemicals using the fungus Coniochaeta ligniaria.

Random UV-C mutagenesis of Scheffersomyces (formerly Pichia) stipitis NRRL Y-7124 to improve anaerobic growth on lignocellulosic sugars.

Scheffersomyces (formerly Pichia) stipitis NRRL Y-7124 was mutagenized using UV-C irradiation to produce yeast strains for anaerobic conversion of lignocellulosic sugars to ethanol. UV-C irradiation potentially produces large numbers of random mutations broadly and uniformly over the whole genome to generate unique strains. Wild-type cultures of S. stipitis NRRL Y-7124 were subjected to UV-C (234 nm) irradiation targeted at approximately 40% cell survival. When surviving cells were selected in sufficient numbers via automated plating strategies and cultured anaerobically on xylose medium for 5 months at 28°C, five novel mutagenized S. stipitis strains were obtained. Variable number tandem repeat analysis revealed that mutations had occurred in the genome, which may have produced genes that allowed the anaerobic utilization of xylose. The mutagenized strains were capable of growing anaerobically on xylose/glucose substrate with higher ethanol production during 250- to 500-h growth than a Saccharomyces cerevisiae yeast strain that is the standard for industrial fuel ethanol production. The S. stipitis strains resulting from this intense multigene mutagenesis strategy have potential application in industrial fuel ethanol production from lignocellulosic hydrolysates.

Continuous ethanol production from wheat straw hydrolysate by recombinant ethanologenic Escherichia coli strain FBR5.

Continuous production of ethanol from alkaline peroxide pretreated and enzymatically saccharified wheat straw hydrolysate by ethanologenic recombinant Escherichia coli strain FBR5 was investigated under various conditions at controlled pH 6.5 and 35 °C. The strain FBR5 was chosen because of its ability to ferment both hexose and pentose sugars under semi-anaerobic conditions without using antibiotics. The average ethanol produced from the available sugars (21.9-47.8 g/L) ranged from 8.8 to 17.3 g/L (0.28-0.45 g/g available sugars, 0.31-0.48 g/g sugar consumed) with ethanol productivity of 0.27-0.78 g l(-1)h(-1) in a set of 14 continuous culture (CC) runs (16-105 days). During these CC runs, no loss of ethanol productivity was observed. This is the first report on the continuous production of ethanol by the recombinant bacterium from a lignocellulosic hydrolysate.

Biotechnological production of mannitol and its applications.

Mannitol, a naturally occurring polyol (sugar alcohol), is widely used in the food, pharmaceutical, medical, and chemical industries. The production of mannitol by fermentation has become attractive because of the problems associated with its production chemically. A number of homo- and heterofermentative lactic acid bacteria (LAB), yeasts, and filamentous fungi are known to produce mannitol. In particular, several heterofermentative LAB are excellent producers of mannitol from fructose. These bacteria convert fructose to mannitol with 100% yields from a mixture of glucose and fructose (1:2). Glucose is converted to lactic acid and acetic acid, and fructose is converted to mannitol. The enzyme responsible for conversion of fructose to mannitol is NADPH- or NADH-dependent mannitol dehydrogenase (MDH). Fructose can also be converted to mannitol by using MDH in the presence of the cofactor NADPH or NADH. A two enzyme system can be used for cofactor regeneration with simultaneous conversion of two substrates into two products. Mannitol at 180 g l(-1) can be crystallized out from the fermentation broth by cooling crystallization. This paper reviews progress to date in the production of mannitol by fermentation and using enzyme technology, downstream processing, and applications of mannitol.

Comparison of separate hydrolysis and fermentation and simultaneous saccharification and fermentation processes for ethanol production from wheat straw by recombinant Escherichia coli strain FBR5.

Ethanol production by recombinant Escherichia coli strain FBR5 from dilute acid pretreated wheat straw (WS) by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) was studied. The yield of total sugars from dilute acid (0.5% H(2)SO(4)) pretreated (160 °C, 10 min) and enzymatically saccharified (pH 5.0, 45 °C, 72 h) WS (86 g/l) was 50.0 ± 1.4 g/l. The hydrolyzate contained 1,184 ± 19 mg furfural and 161 ± 1 mg hydroxymethyl furfural per liter. The recombinant E. coli FBR5 could not grow at all at pH controlled at 4.5 to 6.5 in the non-abated wheat straw hydrolyzate (WSH) at 35 °C. However, it produced 21.9 ± 0.3 g ethanol from non-abated WSH (total sugars, 44.1 ± 0.4 g/l) in 90 h including the lag time of 24 h at controlled pH 7.0 and 35 °C. The bioabatement of WS was performed by growing Coniochaeta ligniaria NRRL 30616 in the liquid portion of the pretreated WS aerobically at pH 6.5 and 30 °C for 15 h. The bacterium produced 21.6 ± 0.5 g ethanol per liter in 40 h from the bioabated enzymatically saccharified WSH (total sugars, 44.1 ± 0.4 g) at pH 6.0. It produced 24.9 ± 0.3 g ethanol in 96 h and 26.7 ± 0.0 g ethanol in 72 h per liter from bioabated WSH by batch SSF and fed-batch SSF, respectively. SSF offered a distinct advantage over SHF with respect to reducing total time required to produce ethanol from the bioabated WS. Also, fed-batch SSF performed better than the batch SSF with respect to shortening the time requirement and increase in ethanol yield.

Effects of pH and corn steep liquor variability on mannitol production by Lactobacillus intermedius NRRL B-3693.

Lactobacillus intermedius NRRL B-3693 produced mannitol, lactic acid, and acetic acid when grown on fructose at 37 degrees C. The optimal pH for mannitol production from fructose by the heterofermentative lactic acid bacterium (LAB) in pH-controlled fermentation was at pH 5.0. It produced 160.7 +/- 1.1 g mannitol in 40 h with a volumetric productivity of 4.0 g l(-1) h(-1) in a simplified medium containing 250 g fructose, 50 g corn steep liquor (CSL), and 33 mg MnSO(4) per liter. However, the mannitol production by the LAB was severely affected by the variability of CSL. The supplementation of CSL with soy peptone (5 g/l), tryptophan (50 mg/l), tryptophan (50 mg/l) plus tyrosine (50 mg/l), or commercial protease preparation (2 ml/100 g of CSL) enhanced the performance of the inferior CSL and thus helped to overcome the nutrient limitations.

Efficient itaconic acid production by Aspergillus terreus: Overcoming the strong inhibitory effect of manganese.

Itaconic acid (IA), a building block platform chemical, is produced industrially by Aspergillus terreus utilizing glucose. Lignocellulosic biomass can serve as a low cost source of sugars for IA production. However, the fungus could not produce IA from dilute acid pretreated and enzymatically saccharified wheat straw hydrolyzate even at 100-fold dilution. Furfural, hydroxymethyl furfural and acetic acid were inhibitory, as is typical, but Mn2+ was particularly problematic for IA production. It was present in the hydrolyzate at a level that was 230 times over the inhibitory limit (50 ppb). Recently, it was found that PO43- limitation decreased the inhibitory effect of Mn2+ on IA production. In the present study, a novel medium was developed for production of IA by varying PO43- , Fe3+ and Cu2+ concentrations using response surface methodology, which alleviated the strong inhibitory effect of Mn2+ . The new medium contained 0.08 g KH2 PO4 , 3 g NH4 NO3 , 1 g MgSO4 ·7H2 O, 5 g CaCl2 ·2 H2 O, 0.83 mg FeCl3 ·6H2 O, 8 mg ZnSO4 ·7H2 O, and 45 mg CuSO4 ·5H2 O per liter. The fungus was able to produce IA very well in the presence of Mn2+ up to 100 ppm in the medium. This medium will be extremely useful for IA production in the presence of Mn2+ . This is the first report on the development of Mn2+ tolerant medium for IA production by A. terreus.

Factors Affecting Production of Itaconic Acid from Mixed Sugars by Aspergillus terreus.

Itaconic acid (IA; a building block platform chemical) is currently produced industrially from glucose by fermentation with Aspergillus terreus. In order to expand the use of IA, its production cost must be lowered. Lignocellulosic biomass has the potential to serve as low-cost source of sugars for IA production. It was found that the fungus cannot produce IA from dilute acid pretreated and enzymatically saccharified wheat straw hydrolysate even at 100-fold dilution. The effects of typical compounds (acetic acid, furfural, HMF and Mn2+, enzymes, CaSO4), culture conditions (initial pH, temperature, aeration), and medium components (KH2PO4, NH4NO3, CaCl2·2H2O, FeCl3·6H2O) on growth and IA production by A. terreus NRRL 1972 using mixed sugar substrate containing glucose, xylose, and arabinose (4:3:1, 80 g L-1) mimicking the wheat straw hydrolysate were investigated. Acetic acid, furfural, Mn2+, and enzymes were strong inhibitors to both growth and IA production from mixed sugars. Optimum culture conditions (pH 3.1, 33 °C, 200 rpm) and medium components (0.8 g KH2PO4, 3 g NH4NO3, 2.0 g CaCl2·2H2O, 0.83-3.33 mg FeCl3·6H2O per L) as well as tolerable levels of inhibitors (0.4 g acetic acid, < 0.1 g furfural, 100 mg HMF, < 5.0 ppb Mn2+, 24 mg CaSO4 per L) for mixed sugar utilization were established. The results will be highly useful for developing a bioprocess technology for IA production from lignocellulosic feedstocks.

Valorization of egg shell as a detoxifying and buffering agent for efficient polymalic acid production by Aureobasidium pullulans NRRL Y-2311-1 from barley straw hydrolysate.

Stepwise formulation of a versatile and cost-effective medium based on barley straw hydrolysate and egg shell for efficient polymalic acid production by A. pullulans NRRL Y-2311-1 was carried out for the first time. The strain did not grow and produce polymalic acid when dilute acid pretreated barley straw hydrolysate (total fermentable sugars: 94.60 g/L; furfural: 1.01 g/L; hydroxymethylfurfural: 0.55 g/L; acetic acid: 5.06 g/L) was directly used in medium formulation without detoxification (e.g. charcoal pretreatment). When CaCO3 in the medium formulation was substituted with egg shell powder, efficient production of polymalic acid was achieved without a detoxification step. Utilization of 40 g/L of egg shell powder led to 43.54 g polymalic acid production per L with the productivity of 0.30 g/L/h and yield of 0.48 g/g. The bioprocess strategy used in this study can also be utilized for mass production of several other industrially important microbial organic acids and biomaterials.

Efficient production of L-ribose with a recombinant Escherichia coli biocatalyst.

A new synthetic platform with potential for the production of several rare sugars, with l-ribose as the model target, is described. The gene encoding the unique NAD-dependent mannitol-1-dehydrogenase (MDH) from Apium graveolens (garden celery) was synthetically constructed for optimal expression in Escherichia coli. This MDH enzyme catalyzes the interconversion of several polyols and their l-sugar counterparts, including the conversion of ribitol to l-ribose. Expression of recombinant MDH in the active form was successfully achieved, and one-step purification was demonstrated. Using the created recombinant E. coli strain as a whole-cell catalyst, the synthetic utility was demonstrated for production of l-ribose, and the system was improved using shaken flask experiments. It was determined that addition of 50 to 500 microM ZnCl(2) and addition of 5 g/liter glycerol both improved production. The final levels of conversion achieved were >70% at a concentration of 40 g/liter and >50% at a concentration of 100 g/liter. The best conditions determined were then scaled up to a 1-liter fermentation that resulted in 55% conversion of 100 g/liter ribitol in 72 h, for a volumetric productivity of 17.4 g liter(-1) day(-1). This system represents a significantly improved method for the large-scale production of l-ribose.

Cloning, purification, and characterization of a thermostable alpha-L-arabinofuranosidase from Anoxybacillus kestanbolensis AC26Sari.

The gene, AbfAC26Sari, encoding an alpha-L-arabinofuranosidase from Anoxybacillus kestanbolensis AC26Sari, was isolated, cloned, sequenced, and characterized. On the basis of amino acid sequence similarities, this 57-kDa enzyme could be assigned to family 51 of the glycosyl hydrolase classification system. Characterization of the purified recombinant alpha-L-arabinofuranosidase produced in Escherichia coli BL21 revealed that it is active at a broad pH range (pH 4.5 to 9.0) and at a broad temperature range (45-85 degrees C) and it has an optimum pH of 5.5 and an optimum temperature of 65 degrees C. Kinetic experiment at 65 degrees C with p-nitrophenyl alpha-L-arabinofuranoside as a substrate gave a Vmax and Km values of 1,019 U/mg and 0.139 mM, respectively. The enzyme had no apparent requirement of metal ions for activity, and its activity was strongly inhibited by 1 mM Cu2+ and Hg2+. The recombinant arabinofuranosidase released L-arabinose from arabinan, arabinoxylan, oat spelt xylan, arabinobiose, arabinotriose, arabinotetraose, and arabinopentaose. Endoarabinanase activity was not detected. These findings suggest that AbfAC26Sari is an exo-acting enzyme.

Ninety six well microtiter plate as microbioreactors for production of itaconic acid by six Aspergillus terreus strains.

Itaconic acid (IA) is a building block platform chemical that is currently produced industrially from glucose by fermentation with Aspergillus terreus. However, lignocellulosic biomass has the potential to serve as low cost source of sugars for production of IA. Previously, 100 A. terreus strains were evaluated for production of IA from pentose sugars in shake-flasks. Six selected strains were then investigated for IA production in shake-flasks. But none of the strains grew and produced IA using biomass hydrolyzates. In order to study the factors inhibiting fungal growth and IA production, we have evaluated these six strains for sugar utilization and IA production from glucose, xylose, arabinose, mixed sugars, and both dilute acid and liquid hot water pretreated wheat straw hydrolyzates in microtiter plate (MTP) microbioreactors at 100µL scale. The results clearly indicate that MTP is very useful as a convenient, reliable and affordable platform to investigate the reasons for inhibition of growth and IA production by the A. terreus strains and should greatly aid in strain development and optimization of IA production by the fungal strains.

Butanol production from sweet sorghum bagasse with high solids content: Part I-comparison of liquid hot water pretreatment with dilute sulfuric acid.

In these studies, we pretreated sweet sorghum bagasse (SSB) using liquid hot water (LHW) or dilute H2 SO4 (2 g L-1 ) at 190°C for zero min (as soon as temperature reached 190°C, cooling was started) to reduce generation of sugar degradation fermentation inhibiting products such as furfural and hydroxymethyl furfural (HMF). The solids loading were 250-300 g L-1 . This was followed by enzymatic hydrolysis. After hydrolysis, 89.0 g L-1 sugars, 7.60 g L-1 acetic acid, 0.33 g L-1 furfural, and 0.07 g L-1 HMF were released. This pretreatment and hydrolysis resulted in the release of 57.9% sugars. This was followed by second hydrolysis of the fibrous biomass which resulted in the release of 43.64 g L-1 additional sugars, 2.40 g L-1 acetic acid, zero g L-1 furfural, and zero g L-1 HMF. In both the hydrolyzates, 86.3% sugars present in SSB were released. Fermentation of the hydrolyzate I resulted in poor acetone-butanol-ethanol (ABE) fermentation. However, fermentation of the hydrolyzate II was successful and produced 13.43 g L-1 ABE of which butanol was the main product. Use of 2 g L-1 H2 SO4 as a pretreatment medium followed by enzymatic hydrolysis resulted in the release of 100.6-93.8% (w/w) sugars from 250 to 300 g L-1 SSB, respectively. LHW or dilute H2 SO4 were used to economize production of cellulosic sugars from SSB. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:960-966, 2018.

High solid fed-batch butanol fermentation with simultaneous product recovery: Part II-process integration.

In these studies, liquid hot water (LHW) pretreated and enzymatically hydrolyzed Sweet Sorghum Bagasse (SSB) hydrolyzates were fermented in a fed-batch reactor. As reported in the preceding paper, the culture was not able to ferment the hydrolyzate I in a batch process due to presence of high level of toxic chemicals, in particular acetic acid released from SSB during the hydrolytic process. To be able to ferment the hydrolyzate I obtained from 250 g L-1 SSB hydrolysis, a fed-batch reactor with in situ butanol recovery was devised. The process was started with the hydrolyzate II and when good cell growth and vigorous fermentation were observed, the hydrolyzate I was slowly fed to the reactor. In this manner the culture was able to ferment all the sugars present in both the hydrolyzates to acetone butanol ethanol (ABE). In a control batch reactor in which ABE was produced from glucose, ABE productivity and yield of 0.42 g L-1 h-1 and 0.36 were obtained, respectively. In the fed-batch reactor fed with SSB hydrolyzates, these productivity and yield values were 0.44 g L-1 h-1 and 0.45, respectively. ABE yield in the integrated system was high due to utilization of acetic acid to convert to ABE. In summary we were able to utilize both the hydrolyzates obtained from LHW pretreated and enzymatically hydrolyzed SSB (250 g L-1 ) and convert them to ABE. Complete fermentation was possible due to simultaneous recovery of ABE by vacuum. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:967-972, 2018.

Production of itaconic acid from pentose sugars by Aspergillus terreus.

Itaconic acid (IA), an unsaturated 5-carbon dicarboxylic acid, is a building block platform chemical that is currently produced industrially from glucose by fermentation with Aspergillus terreus. However, lignocellulosic biomass has potential to serve as low-cost source of sugars for production of IA. Research needs to be performed to find a suitable A. terreus strain that can use lignocellulose-derived pentose sugars and produce IA. One hundred A. terreus strains were evaluated for the first time for production of IA from xylose and arabinose. Twenty strains showed good production of IA from the sugars. Among these, six strains (NRRL strains 1960, 1961, 1962, 1972, 66125, and DSM 23081) were selected for further study. One of these strains NRRL 1961 produced 49.8 ± 0.3, 38.9 ± 0.8, 34.8 ± 0.9, and 33.2 ± 2.4 g IA from 80 g glucose, xylose, arabinose and their mixture (1:1:1), respectively, per L at initial pH 3.1 and 33°C. This is the first report on the production of IA from arabinose and mixed sugar of glucose, xylose, and arabinose by A. terreus. The results presented in the article will be very useful in developing a process technology for production of IA from lignocellulosic feedstocks. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1059-1067, 2017.

Biological pretreatment of corn stover with Phlebia brevispora NRRL-13108 for enhanced enzymatic hydrolysis and efficient ethanol production.

Biological pretreatment of lignocellulosic biomass by white-rot fungus can represent a low-cost and eco-friendly alternative to harsh physical, chemical, or physico-chemical pretreatment methods to facilitate enzymatic hydrolysis. In this work, solid-state cultivation of corn stover with Phlebia brevispora NRRL-13018 was optimized with respect to duration, moisture content and inoculum size. Changes in composition of pretreated corn stover and its susceptibility to enzymatic hydrolysis were analyzed. About 84% moisture and 42 days incubation at 28°C were found to be optimal for pretreatment with respect to enzymatic saccharification. Inoculum size had little effect compared to moisture level. Ergosterol data shows continued growth of the fungus studied up to 57 days. No furfural and hydroxymethyl furfural were produced. The total sugar yield was 442 ± 5 mg/g of pretreated corn stover. About 36 ± 0.6 g ethanol was produced from 150 g pretreated stover per L by fed-batch simultaneous saccharification and fermentation (SSF) using mixed sugar utilizing ethanologenic recombinant Eschericia coli FBR5 strain. The ethanol yields were 32.0 ± 0.2 and 38.0 ± 0.2 g from 200 g pretreated corn stover per L by fed-batch SSF using Saccharomyces cerevisiae D5A and xylose utilizing recombinant S. cerevisiae YRH400 strain, respectively. This research demonstrates that P. brevispora NRRL-13018 has potential to be used for biological pretreatment of lignocellulosic biomass. This is the first report on the production of ethanol from P. brevispora pretreated corn stover. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:365-374, 2017.

Ethanol production from alkaline peroxide pretreated enzymatically saccharified wheat straw.

Wheat straw used in this study contained 44.24 +/- 0.28% cellulose and 25.23 +/- 0.11% hemicellulose. Alkaline H(2)O(2) pretreatment and enzymatic saccharification were evaluated for conversion of wheat straw cellulose and hemicellulose to fermentable sugars. The maximum yield of monomeric sugars from wheat straw (8.6%, w/v) by alkaline peroxide pretreatment (2.15% H(2)O(2), v/v; pH 11.5; 35 degrees C; 24 h) and enzymatic saccharification (45 degrees C, pH 5.0, 120 h) by three commercial enzyme preparations (cellulase, beta-glucosidase, and xylanase) using 0.16 mL of each enzyme preparation per g of straw was 672 +/- 4 mg/g (96.7% yield). During the pretreatment, no measurable quantities of furfural and hydroxymethyl furfural were produced. The concentration of ethanol (per L) from alkaline peroxide pretreated enzyme saccharified wheat straw (66.0 g) hydrolyzate by recombinant Escherichia coli strain FBR5 at pH 6.5 and 37 degrees C in 48 h was 18.9 +/- 0.9 g with a yield of 0.46 g per g of available sugars (0.29 g/g straw). The ethanol concentration (per L) was 15.1 +/- 0.1 g with a yield of 0.23 g/g of straw in the case of simultaneous saccharification and fermentation by the E. coli strain at pH 6.0 and 37 degrees C in 48 h.