Energy-saving direct ethanol production from viscosity reduction mash of sweet potato at very high gravity (VHG)

Sweet potato is an important dietary and economic material in China (accounting for 85% of global production in 2005) and Southeast Asia. The limitation of using root and tuber of sweet potato mash at high solids content is attributed to its high viscous nature. The aim of this study was to investigate the influence of different viscosity reduction factors and found optimal parameters via a surface response design. The optimal xylanase enzyme dose, pretreatment time and temperature were 1.56 AGU/g, 87.6 min and 44.1 °C, respectively. Using pretreatment sweet potato mash on the optimized condition, the final viscosity 498.1 cp and ethanol yield of 135.1 g/kg was obtained by Saccharomyces cerevisiae, which was equivalent to 90.7% of the theoretical yield.     

A novel aeration strategy in repeated-batch fermentation for efficient ethanol production from sweet sorghum juice

To improve the efficiency of ethanol production in a batch fermentation from sweet sorghum juice under a very high gravity(VHG) condition(～ 290 g/L of total sugar) by Saccharomyces cerevisiae NP01, repeatedbatch fermentation under an aerated condition(2.5 vvm for the first 4 h during every cycle) was done in a5-L fermenter. The average ethanol concentration(P), productivity(Qp) and yield(Yp/s) for five successive cycles were 112.31 g/L, 1.55 g/L·h~(-1) and 0.44, respectively with 80.97% sugar consumption. To complete sugar consumption, the total sugar of the juice was reduced to a high gravity(HG) level(～240 g/L). The results showed that yeast extract was not necessary for ethanol production, and aeration during every other cycle i.e., alternating cycles, was sufficient to promote both yeast growth and ethanol production.The average P, Qpand Yp/svalues for eight successive cycles with aeration during alternating cycles were97.58 g/L, 1.98 g/Láh and 0.41, respectively with 91.21% sugar consumption. The total fatty acids in the yeast cells under the aerated condition were ～ 50% higher than without aeration, irrespective the initial sugar concentration, whereas the ergosterol contents under aeration condition were ～ 29% to 49% higher than those without aeration.     

气提法弱化超高浓度乙醇发酵过程中自絮凝酵母振荡行为

超高浓度(very high gravity,VHG)连续乙醇发酵过程中的振荡行为会导致发酵终点的乙醇浓度振荡和降低,是VHG连续乙醇发酵面临的主要问题。研究表明,游离酵母Saccharomyces cerevisiae 4126和自絮凝酵母BHL01在VHG连续乙醇发酵过程中,生物量、残糖、乙醇、甘油等发酵参数都呈现130～145 h的周期性振荡,且絮凝酵母发酵体系的平均乙醇浓度和乙醇生产强度都明显高于游离酵母体系。在絮凝酵母VHG连续乙醇发酵过程中利用发酵尾气气提分离乙醇,酵母细胞振荡行为被明显弱化,达到拟稳态状态,并且使发酵液中的残糖浓度控制在0.1 g·L^-1以下,平均乙醇浓度为110.87 g·L^-1,乙醇产率达到2.99 g·L^-1·h^-1。因此,本研究为弱化VHG连续乙醇发酵中的参数振荡行为提供了新的技术手段。     

乙醇浓醪发酵技术研究进展

乙醇浓醪发酵具有高细胞密度、高产物浓度和高生产速率等特点,是乙醇工业的发展目标和方向。采用乙醇浓醪发酵技术,具有节约工艺用水、提高设备利用率、降低能耗等优势,是提高乙醇发酵工业效益的重要途径。研究乙醇浓醪发酵具有十分重要的现实意义。本文综述了乙醇浓醪发酵技术研究进展,介绍了乙醇浓醪发酵定义、优势以及影响乙醇浓醪发酵的因素。指出降低发酵醪液黏度、筛选高耐性酿酒酵母、改变发酵工艺模式、添加适宜酶制剂以及营养物质是实现乙醇浓醪发酵技术的主要途径,其中筛选高耐性的酿酒酵母是实现乙醇浓醪发酵技术的关键。     

培养基优化以促进超高浓度发酵生产乙醇(英文)

An optimal medium (300 g·L-1 initial glucose) comprising 6.3 mmol·L-1 Mg2+, 5.0 mmol·L-1 Ca2+, 15.0 g·L-1 peptone and 21.5 g·L-1 yeast extract was determined by uniform design to improve very high gravity (VHG) ethanol fermentation, showing over 30% increase in final ethanol (from 13.1% to 17.1%, by volume), 29% decrease in fermentation time (from 84 to 60 h), 80% increase in biomass formation and 26% increase in glucose utilization. Experiments also revealed physiological aspects linked to the fermentation enhancements. Compared to the control, trehalose in the cells grown in optimal fermentation medium increased 17.9-, 2.8-, 1.9-, 1.8- and 1.9-fold at the fermentation time of 12, 24, 36, 48 and 60 h, respectively. Its sharp rise at the early stage of fermentation when there was a considerable osmotic stress suggested that trehalose played an important role in promoting fermentation. Meanwhile, at the identical five fermentation time, the plasma membrane ATPase activity of the cells grown in optimal medium was 2.3, 1.8, 1.6, 1.5 and 1.3 times that of the control, respectively. Their disparities in enzymatic activity became wider when the glucose levels were dramatically changed for ethanol production, suggesting this enzyme also contributed to the fermentation improvements. Thus, medium optimization for VHG ethanol fermentation was found to trigger the increased yeast trehalose accumulation and plasma membrane ATPase activity.     

甘薯渣发酵乙醇的工艺研究

研究了甘薯渣同步糖化发酵乙醇的最佳工艺条件,考察了不同酵母接种量、水料比、发酵时间和 pH 对甘薯渣发酵乙醇的影响。通过单因素、正交试验,最终确定同步糖化发酵乙醇的最佳条件为：接种量1.4%,水料比25：1,发酵时间108h,pH 5.5。在此条件下乙醇得率为34.78%,糖利用率为73.76%。     

超高浓度(VHG)乙醇发酵研究进展

简要介绍了超高浓度乙醇发酵的特点及面临的困难,对VHG乙醇发酵国内外研究进展进行了综述,同时对该领域发展的前景进行了分析和展望。     

Protective Effect of Encapsulation in Fermentation of Limonene-contained Media and Orange Peel Hydrolyzate

This work deals with the application of encapsulation technology to eliminate inhibition by D-limonene in fermentation of orange wastes to ethanol. Orange peel was enzymatically hydrolyzed with cellulase and pectinase. However, fermentation of the released sugars in this hydrolyzate by freely suspended S. cerevisiae failed due to inhibition by limonene. On the other hand, encapsulation of S. cerevisiae in alginate membranes was a powerful tool to overcome the negative effects of limonene. The encapsulated cells were able to ferment the orange peel hydrolyzate in 7 h, and produce ethanol with a yield of 0.44 g/g fermentable sugars. Cultivation of the encapsulated yeast in defined medium was successful, even in the presence of 1.5% (v/v) limonene. The capsules’ membranes were selectively permeable to the sugars and the other nutrients, but not limonene. While 1% (v/v) limonene was present in the culture, its concentration inside the capsules was not more than 0.054% (v/v).     

Application of full permeate recycling to very high gravity ethanol fermentation from corn

A ceramic membrane with pore size of 0.2 μm was used to percolate grain stillage of very high gravity (VHG) ethanol fermentation from corn, and the micro-filtration permeate was completely recycled for the cooking step in the next fermentation process. The concentrations of solids, sugars, total nitrogen and Na⁺ in the grain stillage and permeate reached a relative steady state after two or three batches of filtration and recycling process. There are no negative effects of by-products on VHG ethanol fermentation, and the final ethanol yield was above 15% (v/v). The conditions of filtration were examined to determine the optimum conditions for the process and included an initial flux of clean water above 550 L·m⁻²·h⁻¹ (0.1 MPa), an operating differential pressure of 0.15 MPa, an operating temperature above 70 °C, and a permeation flux greater than 136 L·m⁻²·h⁻¹. It could be concluded that full permeate recycling during ethanol production was an efficient process that resulted in less pollution and less energy consumption. Zhongyang Ding and Liang Zhang made equal contribution to this research.     

我国甘薯生产燃料乙醇的工艺现状及脱水技术改进

介绍了我国甘薯生产燃料乙醇的必要性及其优势,详细介绍了甘薯燃料乙醇的工艺现状,并针对现行工艺中脱水技术的不足,通过实验探索提出一套完全由甘薯构成的燃料乙醇制备过程,重点改进了原工艺的吸附脱水技术,提高了甘薯的综合利用率,为工业化生产甘薯燃料乙醇的绿色工艺提供新思路.     

FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.     

Simultaneous saccharification and fermentation of pretreated Antigonum leptopus (Linn) leaves to ethanol

Simultaneous saccharification and fermentation (SSF) of alkaline hydrogen peroxide pretreated Antigonum leptopus (Linn) leaves to ethanol was optimized using cellulase from Trichoderma reesei QM‐9414 (Celluclast® from Novo) and Saccharomyces cerevisiae NRRL‐Y‐132 cells. Contrary to the saccharification optima (2.5% w/v substrate concentration, 50 °C, 4.5 pH, 40 FPU cellulase g⁻¹ substrate and 24 h reaction time), the SSF optima was found to be somewhat different (10% w/v substrate, 40 °C, 100 FPU cellulase g⁻¹ substrate and 72 h). Better ethanol yields were obtained with SSF compared with the traditional saccharification and subsequent fermentation (S&F) and when the cellulase was supplemented with β‐glucosidase. © 1999 Society of Chemical Industry     

Extraction of bioethanol from fermented sweet sorghum bagasse by batch distillation

Extraction of bioethanol, a potential alternative to fossil fuel in the transport industry, from sweet sorghum stems [Sorghum bicolor (L.) Moench] using solid-state fermentation (SSF) technology has become a popular research topic worldwide. Because SSF technology can directly convert fermentable sugars into target products without juice squeezing and water input, this method can potentially reduce energy and water consumption. However, ethanol extraction from fermented sweet sorghum bagasse requires further investigation. We used batch solid-state distillation to investigate the optimal operating parameters in a distillation column (diameter, 400 mm) via a single-factor experiment. Results showed that the optimal steam flow rate and loading height were 8-10 kg·h^?1 and 700-1,000 mm, respectively. Under optimal conditions, an energy consumption of 3.82 tons of steam per ton of ethanol and distillate concentration of 60.9% (v/v) were obtained. The pseudo-first-order rate equation was used to describe the distillation kinetics, and good correlations were obtained. Therefore, solid-state distillation can be effectively used to extract ethanol from fermented sweet sorghum bagasse.     

Production of L‐lactic acid with very high gravity distillery wastewater from ethanol fermentation by a newly isolated Enterococcus hawaiiensis

BACKGROUND: A great amount of wastewater with high contents of chemical oxygen demand (COD) are produced by ethanol production. It would be useful to utilize distillery wastewater to produce L‐lactic acid, which could be a high additional value byproduct of ethanol production. The fermentation process of L‐lactic acid production by a newly isolated Enterococcus hawaiiensis CICIM‐CU B0114 is reported for the first time. RESULTS: The strain produced 56 g L^?1 of L‐lactic acid after cultivation for 48 h in optimized medium consisting of (g L^?1) 80 glucose, 10 peptone, 10 yeast extract, 1.5 Na₂HPO₄ and 0.2 MgSO₄. E. hawaiiensis CICIM‐CU B0114 was isolated and purified by subculture for growing and producing L‐lactic acid in distillery wastewater of very high gravity (VHG) from ethanol fermentation. L‐lactic acid fermentation was further studied with distillery wastewater substrate in 7 L and 15 L fermentors. The results showed that L‐lactic acid concentrations of 52 g L^?1 and 68 g L^?1 was achieved in 7 L and 15 L fermentors with the initial sugar concentrations of 67 g L^?1 and 87 g L^?1, respectively. CONCLUSION: The production of L‐lactic acid by the newly isolated E. hawaiiensis CICIM‐CU B0114 was carried out and the fermentation medium was optimized by orthogonal experimental design. This new strain holds the promise of L‐lactic acid production utilizing distillery wastewater from VHG ethanol fermentation. Copyright © 2010 Society of Chemical Industry     

FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.     

氧化还原电位控制下自絮凝酵母高浓度乙醇发酵

控制自絮凝酵母高浓度乙醇发酵过程的氧化还原电位（oxidoreduction potential, ORP）能降低环境胁迫对细胞的影响,提高乙醇生产强度和乙醇收率。实验考察了初始糖浓度为200、250、300 g·L^-1及ORP控制为-100、-150 mV和不控制的乙醇发酵情况。结果表明控制ORP的发酵过程,生物量和细胞存活率均高于不控制的系统,相应的发酵速度得到了提高,但是乙醇对糖的收率存在最优值。在实验设定初始糖浓度最高的300 g·L^-1的发酵过程中,控制ORP为-150 mV时,取得了最大的净乙醇生成量和乙醇对糖的收率。ORP控制改变了絮凝颗粒的粒径分布,运用多元线性拟合,发现ORP对絮凝的影响是正向的。ORP改变了发酵液中生物量及代谢物的浓度而间接影响了细胞的絮凝状况。     

玉米秸秆生物法制取酒精的中间试验

建立了玉米秸秆采用蒸汽爆破预处理、纤维素酶水解和戊糖己糖同步发酵技术制取酒精的中间试验装置。玉米秸秆在1.6～2.0 MPa条件下蒸汽爆破预处理,在提高玉米秸秆对纤维素酶可及度的同时,玉米秸秆中纤维素、木聚糖和木质素损失分别为4.08%、40.02%和9.91%。里氏木霉以10%的原料制备纤维素酶,并用于降解剩余的90%的原料,滤纸酶活力和纤维素酶水解得率分别为2.27 FPIU/mL和71.3%。初始还原物浓度为43.65 g/L的水解糖液经树干毕赤酵母发酵16 h,还原物利用率和酒精得率分别为87.17%和0.43 g/g(酒精/消耗的糖)。     

Ethanol production from sweet sorghum residual

In this work, the ethanol production from sweet sorghum residue was studied. Sweet sorghum residue was hydrolyzed with phosphoric acid under mild conditions. The liquid hydrolysate was fermented by Pachysolen tannophilus, and the hydrolysis residue was fermented by the simultaneous saccharification and fermentation (SSF) using Saccharomyces cerevisiae with cellulase (60 FPU/g dry materials). Orthogonal experiments were carried out to investigate the effects of main reaction condition factors, such as temperature, acid concentration, time and dry-matter content, on the reducing sugar yield. The results show that the optimal reaction conditions should be 120°C, 80 g/L, 80 min and 10%, respectively. Under these conditions, 0.3024 g reducing sugar/g dry material was obtained. The liquid hydrolysate was then fermented by P.tannophilus with the highest ethanol concentration of 14.5 g/L. At a water-insoluble solid concentration of 5%, 5.4 g/L ethanol was obtained after 12 h of SSF. The total ethanol yield was 0.147 g/g dry material, which would be beneficial for the application of ethanol production from sweet sorghum residue. __________ Translated from Journal of Beijing University of Chemical Technology, 2007, 34(6): 637-639, 652 [译自: 北京化工大学学报]     

冰糖橙皮渣发酵产燃料乙醇的工艺优化

采用纤维素酶、果胶酶和β-葡萄糖苷酶对冰糖橙皮渣进行水解,所得还原糖液接种异常毕赤酵母进行发酵,考察了酵母接种量、发酵时间、pH和发酵温度等单因素对乙醇得率的影响。单因素结果表明:接种量为12%、发酵时间72 h、pH 4.5、发酵温度33℃时乙醇得率最高。在此基础上设计L9(34)正交实验。结果表明,最佳工艺条件为pH 4.5,接种量12%,发酵时间72 h,发酵温度30℃。在此条件下乙醇产率为0.2451 g/g,显著高于单因素实验(0.2263 g/g)和正交实验结果(0.2329 g/g)。     

Development of a new cleaner production process for cassava ethanol

A new cleaner production process for cassava ethanol has been developed, in which the thin stillage by-product was treated initially by anaerobic digestion, and the digestate further processed by hydrogen-form cation exchange resin before being recycled as process water to make mash for the next ethanol fermentation batch. Thuswastewaterwas eliminated and freshwater and energy consumptionwas significantly reduced. To evaluate the new process, ten consecutive batches of ethanol fermentation and anaerobic digestion at lab scale were carried out. Average ethanol production in the recycling batches was 11.43% (v/v) which was similar to the first batch,where deionized (DI)waterwas used as process water. The chemical oxygen demand (COD) removal rate reached 98% and the methane yield was 322 ml per gramof COD removed, suggesting an efficient and stable operation of the anaerobic digestion. In conclusion, the application of the new process can contribute to sustainable development of the cassava ethanol industry.