Extrusion Cooking of Cassava Starch for Ethanol Production

Response surface methodology was used to study the effect of extrusion variables on gelatinization and viscosity of cassava starch with the aim to reduce energy consumption in alcohol production. None of the variables significantly affected the degree of gelatinization and moisture content of starch was the only significant variable affecting cold viscosity. Torque was affected by all the variables moisture being the most important. Extrusion was an efficient pre-treatment for simultaneous saccharification and fermentation of cassava starch, resulting in 92.4% ethanol conversion. The best conditions for continuous process were: 100°C. 70 rpm, 4 mm die opening and 25-27% moisture. For discontinuous process, when the extruded starch would be dried and ground 200°C, 190 rpm, 4 mm die opening and 20% moisture is recommended.     

Fermentation of Cassava Starch Hydrolysate with Immobilised Cells of Saccharomyces cerevisiae

Fermentation of cassava starch hydrolysate with immobilised cells of Saccharomyces cerevisiae (Strain 2177) was carried out. Kieselguhr and brick powder were the substrates used for immobilisation of yeast cells. The pattern of fermentation was followed by the rate of fall in reducing sugar content and the cell growth. The results obtained showed that variations in the immobilised yeast cell preparations did not produce any effect on the rate of reduction of sugars during the fermentation. The final cell densities obtained after 48 h also did not depend on the initial immobilised cell concentration. However it was shown that fermentation could be completed in 48 h. It was also evident from the results that the cells were alive on the support used for immobilisation even after 4 cycles of fermentation.     

Volatile Bio-ester Production from Orange Pulp-Containing Medium Using Saccharomyces cerevisiae

The dynamics of orange pulp (OP) as a fermentation feedstock for the production of volatile esters of “fruity” aroma by using a commercial wine yeast strain (Saccharomyces cerevisiae var. cerevisiae) was investigated. To achieve this goal, the kinetic behaviour of yeast (cell growth, substrate assimilation and volatile ester formation) was studied in OP complemented with nutritive medium under two different aeration conditions. The results were compared with those obtained from conventional processes in nutritive medium containing glucose as a sole carbon source. The results obtained revealed that the yeast cells were able to grow in the OP-containing medium after a 12-h lag period, probably due to the inhibitory effect of limonene. OP was found to stimulate the de novo synthesis of isoamyl acetate, phenylethyl acetate and ethyl esters (hexanoate, octanoate, decanoate and dodecanoate) by S. cerevisiae. This was strongly evident in the case of limited oxygen supply. Based on the above findings, OP appears to be a promising choice for bioflavour production by yeast.     

利用低温蒸煮工艺进行高浓度酒精发酵

本研究利用低温蒸煮工艺,探讨了玉米淀粉的高浓度酒精发酵。在80℃下对玉米粉进行蒸煮15min,同时加α—淀粉酶进行液化。经冷却后,在55℃下加糖化酶糖化30min。再度冷却到30℃,加酵母菌悬液发酵70h。并利用这一技术研究了产高浓度酒精酵母菌株的最佳发酵条件。在加糖化酶量200～300u/g原料。酵母接种量为3％(v/v),发酵温度为30℃,pH4～4.5,发酵周期为70h,原料水比为1:2条件下,所选用的菌株之一W_4可以产生17.5％(v/v)乙醇。发现该菌株在发酵速度和耐酒精能力方面明显地优于国内酒精厂常用的酵母菌株1300。在发酵结束时,成熟发酵醪的pH值为4.2。外观糖度为0(Bx),残还原糖为0.19％,残总糖为3.6％,淀粉利用率为90％。     

Ethanol production from carob pods by Saccharomyces cerevisiae

The production of ethanol from carob pods extract by Saccharomyces cerevisiae in static and shake flask fermentation was investigated. Shake flask fermentation proved to be a better fermentation system for the production of ethanol than static fermentation. The external addition of nutrients into the carob pods extract did not improve the production of ethanol. The maximum concentration of ethanol (75 g/l) was obtained at an inoculum amount of 0.3%, a pH of 4.5, 30°C and an initial sugar concentration of 200 g/1. Under the same fermentation conditions both sterilized and non‐sterilized carob pods extract gave the same final ethanol concentration.     

利用淀粉的啤酒酵母工程菌研究进展

简要概述了利用淀粉的啤酒酵母工程菌的构建、外源淀粉酶基因在工程菌中的遗传稳定性及其表达和分泌淀粉水解酶问题的研究现状 ,分析了目前存在的问题 ,提出了今后的研究方向 ,并展望了其应用前景。     

高乙醇转化率酿酒酵母工程菌株构建研究进展

酿酒酵母(Saccharomyces cerevisiae)发酵产生乙醇的过程中,甘油的生成所消耗的碳源约占总碳源的4%~10%。减少甘油合成量可提高乙醇产率与碳源利用率。其主要策略是修饰或切除一步或多步代谢反应,或引入外源相关基因以改变碳流方向与碳流量,从而使反应向有利于生成更多乙醇而少生成甘油的方向进行。文中主要综述了近年来通过代谢工程手段阻断酿酒酵母甘油的合成或降低甘油的合成量,以提高乙醇发酵糖醇转化率的研究进展。     

甘蔗汁发酵生产乙醇的酿酒酵母的选育

以酿酒酵母YS菌株通过TCC平板初筛,进行酵母性能测定及发酵试验,选育出较适应于甘蔗汁发酵的YS3酵母菌株.     

在酿酒酵母中共表达sXYLA和XKS1及木糖发酵的初步研究

为改善重组酵母发酵木糖生产乙醇的能力,将定点突变改造后的Thermus thermophilus木糖异构酶基因sXYLA克隆到酵母表达载体pYX212并用于转化酸酒酵母Saccharomyces cerevisiae YPH499进行表达研究。酶活检测表明,改造后的木糖异构酶活性是未改造的1.91倍。在此基础上将改造后具有良好特性的木糖异构酶基因sXYLA和来自酸酒酵母的木酮糖激酶基因XKS1耦联,构楚得到重组表达质粒pYX-sXYLA- XKS1,在酿酒酵母YPH499中实现组成型共表达。结果表明,在84 h时重组菌发酵液酶活达到最高,木糖异构酶为0.624 U/mg蛋白,木酮糖激酶为0.688 U/mg蛋白。以葡萄糖和木糖为混合碳源初步进行半通氧发酵,代谢产物分析表明酸酒酵母重组菌木糖的消耗为4.75 g/L,乙醇的产量为0.839 g/L,分别比出发菌提高20.9%和14.8%,为酿酒酵母利用木糖发酵乙醇奠定基础。     

木薯渣分批补料酶水解及酒精发酵的研究

木薯渣是木薯淀粉加工后的废弃物,碳水化合物含量高。实验利用复合酶对木薯渣中淀粉和纤维素等碳水化合物非热水解进行了探索,结果表明:木薯渣具有较好的酶解性能;随着底物浓度的增大,酶解液糖浓度也不断提高,酶解得率逐渐降低;与间歇糖化工艺相比,16%底物在相同的水解条件和相同的酶添加量的条件下,采用4%的起始底物浓度,每隔12 h进行补料,葡萄糖得率从53.6%提高到72.4%;以不添加任何营养物质的水解液为原料进行酒精发酵,24h乙醇浓度达到24.9 g/L,乙醇得率达到42%,发酵效率为82%,乙醇产率达到1.04 g/(L.h),葡萄糖利用率达到97%。     

Processing of Cassava Starch for Adhesive Production

The processing of cassava (Manihot utilissima Pohl) root IITA variety TMS 50395 into starch by varying the steeping period and the effect of these processing methods on the suitability of cassava starch produced for adhesive formulation were investigated. Out of the three processing methods, the one without steeping gave the best starch for adhesive production in terms of the physico-chemical properties such as swelling power. pH, cooking properties, yield, ease of extraction and cost of starch processing. 20% Potassium hydroxide were found to produce the best adhesive product based on the total solids content, pH, colour and applicability.     

Comparative Economics of the Production of High Fructose Syrup from Cassava Chips and Cassava Starch

The higher cost of starch, almost equal to that of cane sugar in International market, necessitates the search for other cheaper raw materials for the production of high fructose syrup at economic cost in countries like India. The direct utilization of cassava chips seems to offer advantages and hence its feasibility was investigated. The comparative economics showed that the gain in lower expenses on cassava chips as compared to cassava starch are completely upset by the higher capital investment on plant and machineries as well as higher expenses on activated carbon and steam. In addition, a number of operational difficulties were encountered with the use of cassava chips. Against the total capital investment of 597.940 and 436.240 US $ for production of 10 t high fructose syrup/d, the cost of production per kg works out to be US $ 0.51 and 0.46, respectively, based on cassava chips and cassava starch. The studies establish that the direct utilization of cassava chips for the production of high fructose syrup does not offer any economic advantage.     

木薯淀粉高温浓醪发酵酒精工艺的研究

以木薯淀粉为原料,以筛选到的耐高温酵母为菌种,进行高温浓醪发酵酒精工艺条件的研究.经单因素、正交实验,得到最佳工艺为:按1∶2的料水比,经液化糖化后,冷却到37℃,调pH为4.0,加入0.10%尿素,接种量为5%,发酵64 h.最高酒度可达15.54%vol.     

Two New S-Phase-Specific Genes from Saccharomyces cerevisiae

Two new yeast genes, ASF1 (Anti-Silencing Function) and ASF2, as well as a C-terminal fragment of SIR3, were identified as genes that derepressed the silent mating type loci when overexpressed. ASF2 overexpression caused a greater derepression than did ASF1. ASF1 overexpression also weakened repression of genes near telomeres, but, interestingly, ASF2 had no effect on telomeric silencing. Sequences of these two genes revealed open reading frames of 279 and 525 amino acids for ASF1 and ASF2, respectively. The ASF1 protein was evolutionarily conserved. MCB motifs, sequences commonly present upstream of genes transcribed specifically in S phase, were found in front of both genes, and, indeed, both genes were transcribed specifically in the S phase of the cell cycle. While an asf2 mutant was viable and had no obvious phenotypes, an asf1 mutant grew poorly. Neither mutant exhibited derepression of the silent mating type loci. The asf1 mutant was sensitive to methyl methane sulfonate, slightly UV-sensitive and somewhat deficient in minichromosome maintenance. It also lowered the restrictive temperature of a cdc13^ts mutant. These phenotypes suggested a role for ASF1 in DNA repair and chromosome maintenance. The GenBank accession numbers for the ASF1 and ASF2 sequences are L07593 and L07649, respectively. © 1997 by John Wiley & Sons, Ltd.     

固定化酵母用于白酒丢糟降解液乙醇发酵的研究

为了提高白酒生产中废弃物的资源化利用效率,探讨了利用固定化酵母实现丢糟降解液连续发酵生产乙醇的工艺。采用固定化的LR3.1300酵母菌株(Saccharomyces sp)进行丢糟降解液的批次和连续乙醇发酵试验。批次发酵试验结果显示,固定化酵母在白酒糟降解液与葡萄糖混合液中发酵的底物利用和产酒效率都较高。在固定化酵母连续发酵中,当固定化酵母液为60 mL,降解糖液进料速度为15 mL/h时,还原糖利用率为83.7%,流出液酒精度达到了3.97%vol,乙醇发酵的效率与前期的游离酵母发酵相比提高了43%。     

Acetylation of Cassava Starch Using Perchloric Acid Catalysis

Acetyl and propionyl derivatives of cassava starch were prepared using perchloric acid catalysis. The temperature for obtaining optimum yield and degree of substitution (DS) was 30°C. The clarity and sol stability of the derivatives are improved, while viscosity is reduced.     

木薯燃料乙醇的原料储藏

木薯收获期集中,不适应车用燃料乙醇企业的连续生产要求,因此进行木薯原料的储藏十分必要。安全的原料储藏水分、符合要求的仓储设施、科学合理的储藏方法、及时正确的问题防治保证了木薯燃料乙醇原料的长期储藏,从而有效解决了“原料集中供应”和“企业连续生产”之间的矛盾。     

两株酵母菌协同酿造黄酒的控制工艺

利用两株酵母菌共同作为菌种制作高温糖化酒母酿造糯米黄酒。前发酵共3 d,落罐后品温达到30.5℃时开头耙30 min,然后分别隔2小时开二耙、三耙各10 min,以后每隔4小时开耙10 min,发酵第5天~10天每天开耙10 min。头耙后0~24 h温控30℃~31℃,24 h~36 h温控29℃~30℃,36 h~48 h温控28℃~29℃,以后每24小时降2℃,温度低于20℃后,按发酵质量降温。发酵22天后,糯米黄酒酒精度为19.4%(体积分数),总糖为1.8 g/L,总酸为5.4 g/L。     

Ethanol from lactose in salted cheese whey by recombinant Saccharomyces cerevisiae

Seven yeast recombinants were selected from 57 fusant colonies on the basis of higher DNA content, nuclear diameter and ethanol yield compared to parental Saccharomyces cerevisiae ATCC 4126 and Kluyveromyces lactis CBS 683. Six recombinants out of the above colonies revealed growth on lactose and sucrose, indicating that they are S. cerevisiae with transformed β-galactosidase systems. The fusant colonies were investigated with respect to their capacity to convert lactose in salted cheese whey into ethanol. Among these recombinants that showed high tolerance towards sodium chloride and higher ethanol yield than lactose fermenting parental K. lactis CBS 683, SK-1 exhibited high tolerance up to 4 g dl^–1 sodium chlonride with an ethanol yield of 4.66 ml dl^–1 (v/v) , SK-23 tolerated 6 g dl^–1 sodium chloride with an ethanol yield of 4.14 ml dl^–1 (v/v) and SK-26 showed resistance towards 8 g dl^–1 sodium chloride and give an ethanol yield of 3 ml dl^–1 (v/v).     

Production of Low Substituted Cassava Starch Acetates and Citrates

Starch acetates and citrates were prepared by treating starch with sodium hydroxide at room temperature with and without 1% concentrated sulphuric acid (per dry weight of starch) as catalyst. Starch acetates were obtained by varying the reaction time (2h, 4h, 6h and 8h) while starch citrates were obtained using citric acid monohydrate conentrations of 5, 10, 15 and 20% (per dry weight of starch). The yields of acetylated starches were greater than those of the starch citrates. Use of catalyst significantly increased the rate and extent of acetylation. Also there were progressive increases in the acetyl values of the catalysed reaction with time. Citrate substitution in catalysed and uncatalysed reactions were not significantly different at citric acid concentrations higher than 10%.