Efficiency of genetically engineered yeast in the production of ethanol from dextrinized cassava starch

Summary The ability of a polyploid/aneuploidSaccharomyces diastaticus spheroplast fusion product and a diploidSaccharomyces diastaticus hybridization product, to produce ethanol from dextrinized cassava starch with varying amounts of supplemented glucoamylase (amyloglucosidase), was investigated. It was found that the added glucoamylase could be reduced by over 50% using these glucoamylase producing strains as compared to a commercially availableSaccharomyces cerevisiae strain commonly used in ethanol producing industries.     

Fermentation of starch to ethanol by an amylolytic yeast Saccharomyces diastaticus SM-10

A total of fifteen yeast strains were isolated from natural sources including fruits, soil, molasses, honey and a variety of indigeneous fermented foods. Screening of these strains for growth, ethanol production and glucoamylase activity led to selection of a yeast strain SM-10 identified as S. diastaticus having maximum glucoamylase activity (80 units ml(-1)) and ethanol production from starch (3.5%). Ethanol production from wheat flour was found to be 1.75% which could be increased to 5.2% after treatment of wheat flour with pepsin, diastase and glucoamylase.     

Fermentation of corn fibre sugars by an engineered xylose utilizing Saccharomyces yeast strain

The ability of a recombinant Saccharomyces yeast strain to ferment the sugars glucose, xylose, arabinose and galactose which are the predominant monosaccharides found in corn fibre hydrolysates has been examined. Saccharomyces strain 1400 (pLNH32) was genetically engineered to ferment xylose by expressing genes encoding a xylose reductase, a xylitol dehydrogenase and a xylulose kinase. The recombinant efficiently fermented xylose alone or in the presence of glucose. Xylose-grown cultures had very little difference in xylitol accumulation, with only 4 to 5g/l accumulating, in aerobic, micro-aerated and anaerobic conditions. Highest production of ethanol with all sugars was achieved under anaerobic conditions. From a mixture of glucose (80g/l) and xylose (40g/l), this strain produced 52g/l ethanol, equivalent to 85% of theoretical yield, in less than 24h. Using a mixture of glucose (31g/l), xylose (15.2g/l), arabinose (10.5g/l) and galactose (2g/l), all of the sugars except arabinose were consumed in 24h with an accumulation of 22g ethanol/l, a 90% yield (excluding the arabinose in the calculation since it is not fermented). Approximately 98% theoretical yield, or 21g ethanol/l, was achieved using an enzymatic hydrolysate of ammonia fibre exploded corn fibre containing an estimated 47.0g mixed sugars/l. In all mixed sugar fermentations, less than 25% arabinose was consumed and converted into arabitol.     

Fermentation of starch to ethanol by a complementary mixture of an amylolytic yeast andSaccharomyces cerevisiae

Summary Synergistic coculture of an amylolytic yeast (Saccharomycopsis fibuligera) andS. cerevisiae, a non-amylolytic yeast, fermented unhydrolyzed starch to ethanol with conversion efficiencies over 90% of the theoretical maximum. Fermentation was optimal between pH 5.0 to 6.0. Using a starch concentration of 10% (w/v) and a 5% (v/v) inoculum ofS. fibuligera, increasingS. cerevisiae inoculum from 4% to 12% (w/v) resulted in 35–40% (w/v) increase in ethanol yields. Anaerobic or limited aerobic incubation almost doubled ethanol yields.     

Kinetics of growth and ethanol production on different carbon substrates using genetically engineered xylose-fermenting yeast

Saccharomyces cerevisiae 424A (LNH-ST) strain was used for fermentation of glucose and xylose. Growth kinetics and ethanol productivity were calculated for batch fermentation on media containing different combinations of glucose and xylose to give a final sugar concentration of 20+/-0.8 g/L. Growth rates obtained in pure xylose-based medium were less than those for media containing pure glucose and glucose-xylose mixtures. A maximum specific growth rate micro(max) of 0.291 h(-1) was obtained in YPD medium containing 20 g/L glucose as compared to 0.206 h(-1) in YPX medium containing 20 g/L xylose. In media containing combinations of glucose and xylose, glucose was exhausted first followed by xylose. Ethanol production on pure xylose entered log phase during the 12-24h period as compared to the 4-10h for pure glucose based medium using 2% inoculum. When glucose was added to fermentation flasks which had been initiated on a pure xylose-based medium, the rate of xylose usage was reduced indicating cosubstrate inhibition of xylose consumption by glucose.     

Ethanol production from corn cob pretreated by the ammonia steeping process using genetically engineered yeast

Summary A new and effective pretreatment process for biomass conversion involves the steeping of biomass in 2.9 M NH₄OH. This resulted in the removing about 80–90% of the lignin along with almost all the acetate from cellulosic residues. Based on dry cellulose from corn cob, a high glucose yield of 92% was obtained after enzymatic saccharification of cellulose fraction. By using a genetically engineered, xylosefermenting Saccharomyces 1400(pLNH33) in the batch fermentation of a glucose-xylose mixture from corn cob, an ethanol concentration of 47 g/L was obtained within 36 h with 84% yield. In addition, an ethanol concentration of 45 g/L was obtained within 48 h with 86% yield using simultaneous saccharification-fermentation process.     

Fermentation of lactose to ethanol with recombinant yeast in an immobilized yeast membrane bioreactor

A novel concept of membrane bioreactor in which living cells are sandwiched between ultrafiltration (UF) and reverse osmosis (RO) membranes was applied for lactose fermentation to ethanol by genetically engineered yeast cells. The productivity of the Lactophile 13B strains was higher than that of the Lactophile 13D strains. In both cases performance data similar to those for glucose fermentation to ethanol by Saccharomyces cerevisiae were obtained. However, the operational stability of recombinant yeast cells was improved in the new bioreactor in comparison to the stability of these cells in a shake flask.     

Industrial yeast strain engineered to ferment ethanol from lignocellulosic biomass

In this study an industrial Saccharomyces cerevisiae yeast strain capable of fermenting ethanol from pretreated lignocellulosic material was engineered. Genes encoding cellulases (endoglucanase, exoglucanase and β-glucosidase) were integrated into the chromosomal ribosomal DNA and delta regions of a derivative of the K1-V1116 wine yeast strain. The engineered cellulolytic yeast produces ethanol in one step through simultaneous saccharification and fermentation of pretreated biomass without the addition of exogenously produced enzymes. When ethanol fermentation was performed with 10% dry weight of pretreated corn stover, the recombinant strain fermented 63% of the cellulose in 96 h and the ethanol titer reached 2.6% v/v. These results demonstrate that cellulolytic S. cerevisiae strains can be used as a platform for developing an economical advanced biofuel process.     

Fermentation of high concentrations of lactose to ethanol by engineered flocculent Saccharomyces cerevisiae

The development of microorganims that efficiently ferment lactose has a high biotechnological interest, particularly for cheese whey bioremediation processes with simultaneous bio-ethanol production. The lactose fermentation performance of a recombinant Saccharomyces cerevisiae flocculent strain was evaluated. The yeast consumed rapidly and completely lactose concentrations up to 150 g l⁻¹ in either well- or micro-aerated batch fermentations. The maximum ethanol titre was 8% (v/v) and the highest ethanol productivity was 1.5–2 g l⁻¹ h⁻¹, in micro-aerated fermentations. The results presented here emphasise that this strain is an interesting alternative for the production of ethanol from lactose-based feedstocks.     

Fermentation of biomass sugars to ethanol using native industrial yeast strains

In this paper, the feasibility of a technology for fermenting sugar mixtures representative of cellulosic biomass hydrolyzates with native industrial yeast strains is demonstrated. This paper explores the isomerization of xylose to xylulose using a bi-layered enzyme pellet system capable of sustaining a micro-environmental pH gradient. This ability allows for considerable flexibility in conducting the isomerization and fermentation steps. With this method, the isomerization and fermentation could be conducted sequentially, in fed-batch, or simultaneously to maximize utilization of both C5 and C6 sugars and ethanol yield. This system takes advantage of a pH-dependent complexation of xylulose with a supplemented additive to achieve up to 86% isomerization of xylose at fermentation conditions. Commercially-proven Saccharomyces cerevisiae strains from the corn-ethanol industry were used and shown to be very effective in implementation of the technology for ethanol production.     

以玉米淀粉糖渣为原料制备米曲发酵酱油

以玉米淀粉糖渣为原料制备米曲,米曲中的中性蛋白酶活力能够达到4000 U/g(干基),糖化酶比活力可达到120 U/g左右,满足酿造酱油所需要求。用糖渣米曲发酵酱油,氨基态氮和总氮质量浓度分别能够达到7.1 g/L和11.9 g/L,还原糖质量浓度为13.2 g/L,各项理化指标均可达到国家二级酱油标准。     

Direct and quantitative conversion of starch to ethanol by the yeast Schwanniomyces alluvius

Summary The yeast Schwanniomyces alluvius ferments soluble starch to ethanol at a conversion efficiency of greater than 95%. Only trace amounts of side products are detectable.NRCC publication no. 20435.     

Fermentation of starch to ethanol by a co-culture of Saccharomycopsis fibuligera and Saccharomyces cerevisiae

Static fermentation of starch to ethanol by a co-culture of Saccharomycopsis fibuligera and Saccharomyces cerevisiae without addition of nutritional supplements was investigated with respect to initial starch concentration, pH of the media and initial dry weight ratio of Sps. fibuligera to Sacc. cerevisiae biomass (I _R).Optimal conditions for ethanol production were: starch from 20 to 30 g/l; initial pH values from 5.8 to 6.0; and I _R values of 2.0 or 3.0. The highest attained ethanol concentration, 13.7 g/l, represented 88% of the theoretical yield.K. Pirelová, D. mogroviová and . Balá are with the Department of Biochemical Technology, Faculty of Chemical Technology, Slovak Polytechnic University, Radlinského 9, 81237 Bratislava, Slovak Republic.     

Fermentation of galacturonic acid and pectin-rich materials to ethanol by genetically modified strains of Erwinia

Evaluation of the four ethanologenic constructs of bacteria in the genus Erwinia indicates that two strains E. chrysanthemi EC16 and E. carotovora SR38 show promise for development of direct hydrolysis and fermentation of pectin-rich substrates to mixtures of ethanol and acetate. Both strains fermented glucose to ethanol in nearly theoretical yields, but produced mainly acetate and ethanol by fermentation of D-galacturonic acid. Both strains depolymerized citrus pectin, polygalacturonic acid and polysaccharides in citrus peel and converted resulting sugars to carbon dioxide, acetate, ethanol and lesser amounts of formate and succinate.     

能利用五碳糖和六碳糖生产乙醇的基因工程菌菌株的构建

燃料乙醇是一种极具前景的燃油代用品,近年来发展尤为迅速,为了推广这种能源和满足日益增长的需求,我们有必要开发更为高效的生产工艺和寻找更为廉价的原料。解决此问题的关键在于获得高效的工程菌,使其能利用木质纤维素水解液中的五碳糖和六碳糖发酵生产乙醇。通过代谢工程的研究和基因重组技术,几种重组细菌显示出良好的开发前景,它们是运动发酵单胞菌、大肠杆菌、产酸克雷伯氏菌和菊欧文氏菌。本文就这四种细菌的研究进展以及基因重组过程进行了介绍和评价。     

Production of ethanol from extruded corn starch by a nonconvencional fermentation method

Summary In single-step 48-hour fermentations of extruded, liquefied and raw corn starch, the yields of ethanol from extruded starch were similar to those from liquefied starch, whereas the yields of ethanol from raw starch were lower.     

Treating cancer with genetically engineered T cells

Administration of ex vivo cultured, naturally occurring tumor-infiltrating lymphocytes (TILs) has been shown to mediate durable regression of melanoma tumors. However, the generation of TILs is not possible in all patients and there has been limited success in generating TIL in other cancers. Advances in genetic engineering have overcome these limitations by introducing tumor-antigen-targeting receptors into human T lymphocytes. Physicians can now genetically engineer lymphocytes to express highly active T-cell receptors (TCRs) or chimeric antigen receptors (CARs) targeting a variety of tumor antigens expressed in cancer patients. In this review, we discuss the development of TCR and CAR gene transfer technology and the expansion of these therapies into different cancers with the recent demonstration of the clinical efficacy of these treatments.     

Sensitivity of genetically engineered organisms to selective media

Eighteen strains of Escherichia coli used in genetic studies were tested for their ability to grow on several selective media. Highest recoveries were obtained with m-T7 agar. The SOS system, particularly the recA gene, may play some role in the sensitivity of E. coli to selective agents. These results may be important in the selection of media used to detect genetically engineered organisms released into the environment.     

Direct production of ethanol from raw corn starch via fermentation by use of a novel surface-engineered yeast strain codisplaying glucoamylase and alpha-amylase

Direct and efficient production of ethanol by fermentation from raw corn starch was achieved by using the yeast Saccharomyces cerevisiae codisplaying Rhizopus oryzae glucoamylase and Streptococcus bovis alpha-amylase by using the C-terminal-half region of alpha-agglutinin and the flocculation functional domain of Flo1p as the respective anchor proteins. In 72-h fermentation, this strain produced 61.8 g of ethanol/liter, with 86.5% of theoretical yield from raw corn starch.