Continuous ethanol production from carob pod extract by immobilized Saccharomyces cerevisiae in a packed-bed reactor

The continuous production of ethanol from carob pod extract by immobilized Saccharomyces cerevisiae in a packed-bed reactor has been investigated. At a substrate concentration of 150 g dm^?3, maximum ethanol productivity of 16 g dm^?3 h^?1 was obtained at D = 0·4 h^?1 with 62·3% of theoretical yield and 83·6% sugars′ utilization. At a dilution rate of 0·1 h^?1, optimal ethanol productivity was achieved in the pH range 3·5–5·5, temperature range 30–35·C and initial sugar concentration of 200 g dm^?3. Maximum ethanol productivity of 24·5 g dm^?3 h^?1 was obtained at D = 0·5 h^?1 with 58·8% of theoretical yield and 85% sugars′ utilization when non-sterilized carob pod extract containing 200 g dm^?3 total sugars was used as feed material. The bioreactor system was operated at a constant dilution rate of 0·5 h^?1 for 30 days without loss of the original immobilized yeast activity. In this case, the average ethanol productivity, ethanol yield (% of theoretical) and sugars′ utilization were 25 g dm^?3 h^?1, 58·8% and 85·5%, respectively.     

Continuous alcohol production from whey permeate using immobilised cell reactor systems

The present paper reports the performance of a bioreactor packed with alginate-entrapped Kluyveromyces marxianus NCYC179 for continuous fermentation of whey permeate to ethanol. A maximum ethanol productivity as 28.21 gl^?1 h^?1 was attained at D=0.42h^?1 and 75% lactose consumption (substrate feed rate in the inflowing medium was 200 g lactose I^?1). However, the higher dilution rates (0.6-1.Oh^?1) resulted in poor productivities and higher substrate washout in the effluent samples. The maximum specific ethanol production (qpi) and maximum specific lactose uptake (qsi) of the immobilised Kluyveromyces marxianus NCYC179 was found to be 3.88g ethanol/g immobilised cell/hx10^?2 and 8.75g lactose consumed/g immobilised cell/hx10^?2 respectively. A bead size of 2.5 mm in diameter and activation period of 24h of alginate beads in lactose solution (10%) prior to their packing in column reactor were found to support the efficient working of the bioreactor. The immobilised cell bioreactor system was operated continuously at a constant dilution rate of 0.15h^?1 and 10% lactose for 562 h without any significant change in the efficiency (varied from 84 to 88% of theoretical) and viability of the entrapped yeast cells (dropped from 84 to 81%).     

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.     

硅橡胶膜生物反应器中乙醇发酵与渗透汽化的耦合

用硅橡胶膜生物反应器(SMBR)实验研究连续发酵-渗透汽化的耦合性能。发酵微生物采用酿酒干酵母,所用碳源为工业级葡萄糖。发酵过程由于产物抑制作用,在乙醇质量浓度达到73 g/L时趋于停滞,而耦合渗透汽化膜后,发酵罐内的乙醇质量浓度降低并维持在40 g/L,使发酵可以连续稳定地进行。在SMBR运行达到稳态后,乙醇的体积产率为4.02 g/(L.h)。发酵液中乙醇质量浓度维持在20~63 g/L,聚二甲基硅氧烷(PDMS)膜的总渗透通量为1 220~800 g/(m2.h),分离因子为5~9.2。与传统发酵和分离相同进料质量分数的乙醇溶液相比,乙醇发酵和渗透汽化在硅橡胶膜生物反应器中能相互耦合并得到强化。与较小规模耦合系统(发酵体积1 L和2 L)比较,性能稳定良好。     

利用Clostridium saccharobutylicum DSM 13864 连续发酵生产丁醇

为使用廉价糖质原料进行连续发酵生产丁醇提供理论依据和实验指导,以Clostridium saccharobutylicum DSM 13864为发酵菌种,考察了稀释率和温度等因素对以葡萄糖为原料的四级连续发酵生产丁醇的影响。结果表明：高稀释率有利于酸的积累和菌体的生长,低稀释率有利于溶剂的生产。当稀释率为0.05 h?1,4个发酵罐温度控制在37 ℃时,总溶剂产量为11.57 g/L,其中丁醇7.29 g/L,生产率为0.145 g/(L?h)。在0.05 h?1稀释率的条件下进行变温连续发酵证实低温有利于溶剂的积累,当一级和二级罐温度控制在37 ℃,三级和四级罐温度控制在33 ℃时总溶剂产量最高为13.69 g/L,其中丁醇为8.36 g/L,生产率为0.171 g/(L?h)。     

不同运行方式对微生物燃料电池处理氨氮废水的影响

微生物燃料电池(MFC)是一种既能去除污染物又能产电的新型污水处理技术,由于其具有利用生物转化能量的节能优势,MFC废水脱氮处理技术引起了更多的关注。本实验在启动MFC的同步硝化与反硝化(SND)后,首先研究了通路与断路条件对MFC产电脱氮的影响,结果表明:断路时有利于硝化反应的发生,氨氮去除率有最大值95.17%;而通路更有利于COD和总氮的去除,表明氮的去除主要依靠阴极接受电子进行。随后分析了曝气阶段+停曝阶段运行方式对MFC产电和脱氮的影响,结果显示:曝气8.5h(DO为4.0mg/L)后停止曝气,停曝阶段为11.5h,DO逐渐降低到2.0mg/L,输出电压由无曝气运行的31mV提高到120mV左右,氨氮去除率最高达到86.42%、总氮去除负荷由无曝气运行的0.064g/(L·d)升高到0.46g/(L·d)。说明曝气阶段+停曝阶段运行方式既能有效提高MFC脱氮产电性能又可以减少维持高浓度DO的能量输入。     

Fuel ethanol production from concentrated food waste hydrolysates in immobilized cell reactors by Saccharomyces cerevisiae H058

BACKGROUND: Continuous ethanol fermentation of concentrated food waste hydrolysates has been studied. The process was carried out in an immobilized cell reactor with beads of calcium‐alginate containing immobilized Saccharomyces cerevisiae H058 at temperature 30 °C and pH 5.0. RESULTS: The total residual sugar decreased with increase of hydraulic retention time (HRT) under various reducing sugar concentrations. Ethanol production by immobilized cells increased with increase in HRT, regardless of the substrate concentrations employed. The highest ethanol concentration of 89.28 g L^?1 was achieved at an HRT of 5.87 h and reducing sugar concentration of 200 g L^?1. At an HRT of 1.47 h, the maximum volumetric ethanol productivity of 49.88 g L^?1 h^?1 and the highest ethanol yield of 0.48 g g^?1 were achieved at reducing sugar concentration of 160 and 200 g L^?1, respectively. The difference between the fresh and the 30‐day Ca–alginate immobilized cell was also shown by scanning electronic micrographs of beads taken from their outer and inner surfaces. CONCLUSIONS: Continuous ethanol production from concentrated food waste hydrolysates using immobilized yeast cells is promising in view of the high ethanol productivity obtained at relatively high conversion and excellent reactor stability. Copyright © 2011 Society of Chemical Industry     

Batch and Continuous Production of Lactic Acid from Beet Molasses by Lactobacillus delbrueckii IFO 3202

Process variables were optimized for the production of lactic acid from pretreated beet molasses by Lactobacillus delbrueckii IFO 3202 for batch and continuous fermentations. In the batch fermentation, maximum yields (95·4% conversion, 77·1% effective) and maximum lactic acid volumetric productivity (4·83 g dm⁻³ h⁻¹) was achieved at 45°C, pH 6·0, 78·2 g dm⁻³ sugar concentration with 10 g dm⁻³ yeast extract. Various cheaper nitrogen sources were replaced with yeast extract on equal nitrogen bases in batch fermentation. Of all the nitrogen sources tested, yeast extract yielded the highest and malt sprouts yielded the second highest level of lactic acid. In the continuous fermentation, maximum lactic acid (4·15%) was obtained at a dilution rate of 0·1 h⁻¹. Maximum volumetric lactic acid productivity (11·20 g dm⁻³ h⁻¹) occurred at D = 0·5 h⁻¹ dilution rate. © 1997 SCI.     

Continuous ethanol fermentation using immobilized yeast in a fluidized bed reactor

Continuous ethanol fermentation of glucose using fluidized bed technology was studied. Saccharomyces cerevisiae were immobilized and retained on porous microcarriers. Over two-thirds of the total reactor yeast cell mass was immobilized. Ethanol productivity was examined as dilution rate was varied, keeping all other experimental parameters constant. Ethanol yield remained high at an average of 0.36 g ethanol g^?1 glucose (71% of theoretical yield) as the dilution rate was increased stepwise from 0.04 h^?1 to 0.14 h^?1. At a dilution rate of 0.15 h^?1, the ethanol yield steeply declined to 0.22 g ethanol g^?1 glucose (44% of theoretical yield). The low maximum percentage of theoretical yield is primarily due to an extended mean cell residence time, and possibly due to the inhibitory effect of a high dissolved carbon dioxide concentration, enhanced by the probable intermittent levels of low pH in the reactor. Constant ethanol production was possible at a high glucose loading rate of 840 g dm^?3 day^?1 (attained at a dilution rate of 0.14 h^?1). Although the highest average ethanol concentration (97.14 g dm^?3) occurred at the initial dilution rate of 0.04 h^?1, the peak average ethanol production rate (2.87 g (g yeast)^?1 day^?1) was reached at a greater dilution rate of 0.11 ^h-1. Thus, the optimal dilution rate was determined to be between 0.11 h^?1 and 0.14 h^?1. Ethanol inhibition on yeast cells was absent in the reactor at average bulk-liquid ethanol concentrations as high as 97.14 g dm^?3. In addition, zero-order kinetics on ethanol production and glucose utilization was evident.     

Continuous production of poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate): Effects of C/N ratio and dilution rate on HB/HV ratio

Ralstonia eutropha was cultivated in a continuous stirred fermenter with various C/N ratios (20, 30, and 40), dilution rates, and organic salt substrates (sodium propionate or sodium valerate) to explore the microbial growth and the poly(3HB-co-3HV) accumulation. When sodium propionate was used as the secondary carbon source, the HB/HV molar ratio at various C/N ratios and dilution rates did not change appreciably (approximately 90: 10). The highest poly(3HB-co-3HV) content in biomass (41.8%) and poly(3HB-co-3HV) productivity (0.100 g/(L·h)) occurred under the condition with a C/N ratio of 20 and dilution rate of 0.06 h⁻¹. When sodium valerate was used as the secondary carbon source, the productivity of poly(3HB-co-3HV) increased with increasing dilution rate for the C/N ratio of 30 and 40. The average HB/HV molar ratio ranged from 48: 52 to 78: 32. The feeding of sodium valerate promoted the accumulation of HV better than feeding sodium propionate did. This study shows that a potential strategy of manipulating by both C/N ratio and dilution rate could be used to control the HV unit fraction in poly(3HB-co-3HV) in a continuous cultivation.     

拟薄水铝石-海藻酸铝固定化酵母生产乙醇

在原位合成拟薄水铝石中加入酵母和海藻酸钠,搅拌并冷冻后制备固定化酵母,以甘蔗废糖蜜生产乙醇。通过复合材料固定化酵母增殖机理发现,固定化酵母数达4.1×109个/mL,批式发酵中14h消耗了90.5%的总糖;40d连续流动中,稀释率为0.100h-1时,最大载体乙醇产率为52.0g/(L.h)。SEM表征表明,该固定化酵母细胞密度高,孔道结构丰富,利于细胞的繁殖生长和物质传送。乙醇发酵过程彻底,速率快,残糖水平低,原料利用率和发酵醪乙醇质量浓度均超过传统工艺。     

Amylolytic enzymes produced by Bacillus amyloliquefaciens MIR-41 in batch and continuous culture

Bacillus amyloliquefaciens MIR-41 has been isolated from natural sources and characterized using statistical methods. The strain showed three types of glucanase activities: α-amylase, α-glucosidase and pullulanase in defined medium and starch as carbon source. Extracellular activity of α-amylase was approximately three times higher in continuous culture than in batch. Maximal productivity was found at a dilution rate of 0·16 h^?1. Alpha-glucosidase was expressed as a cell-bound enzyme in batch culture, but in continuous culture was mostly extracellular. Pullulanase was cell-bound in all cases. The expression of the enzymes was dependent upon the system and the dilution rate used. No cell lysis was detected in the chemostat as compared with batch cultures.     

Increase of ethanol productivity in an airlift reactor with a modified draught tube

Static mixers were introduced in the draught tube of a three-phase, concentric tube type airlift bioreactor, resulting in a 30% increase in ethanol productivity during glucose fermentation with a highly flocculent strain of Saccharomyces cerevisiae. Increased productivity was obtained as a consequence of the floe size reduction provoked by the new design of the draught tube and of the smaller applied aeration rates, allowing a higher dilution rate to be used. Steady state data at different dilution rates were measured for both systems and the results were compared in terms of specific consumption / production rates and ethanol productivity. An approach based on heterogeneous catalysis principles was used in order to consider the presence of porous yeast flocs. Total glucose conversion was achieved at a dilution rate of 0.34 h^?1. The smaller floe size contributed to the higher observed reaction rates by reducing diffusional limitations inside the flocs. The respiratory quotient had a constant value (around 23) at all dilution rates, meaning that the metabolic state of the cells in the flocs remained constant, having a strong fermentative metabolism.     

严格厌氧发酵体系在线尾气监测系统的设计及在梭菌生产生物能源丁醇的应用

目前关于有氧或微氧的乙醇发酵的尾气检测系统已经建立,但是对于丙酮丁醇梭菌等严格厌氧菌发酵尾气的在线监测鲜见文献报道。因此,本研究以丙酮丁醇梭菌生产丁醇的严格厌氧发酵体系为研究对象,研究了传统有氧或微氧尾气检测方法在丙酮丁醇梭菌厌氧发酵体系中的检测结果,设计并建立了适合厌氧菌发酵的尾气在线监测系统,对丙酮丁醇梭菌的发酵过程实时监测。在建立有效的厌氧发酵尾气分析系统的条件下,比较了丙酮丁醇梭菌在游离细胞条件下和高细胞密度条件下的发酵性能。相比较于游离发酵,高细胞密度发酵的发酵周期明显缩短,丁醇生产强度显著提高。丁醇最高产量为15.4g/L,生产强度0.64g/（L·h）,分别比对照组提高了12.4%和106%,CO₂和H₂最高产气速率分别提高60%和9%,产气量分别提高了20.7%和41.3%。尾气分析系统采集的气体数据为丙酮丁醇梭菌的代谢分析提供了重要依据。     

Production of cyclodextrin glycosyltransferase by batch and chemostat culture of Bacillus macerans in chemically defined medium

A chemically defined medium for cultivation of Bacillus macerans is reported. Growth rates and cyclodextrin glycosyltransferase (CGT) titres obtained were similar to those obtained using media containing potato extract. The proteins in supernatant fluids from a batch culture were separated by disc electrophoresis and results obtained showed that CGT was produced after growth ceased, in agreement with results of activity measurements. The maximum growth rate in the chemostat considerably exceeded that in batch culture; this anomalous effect is unexplained. High CGT titres were produced at low dilution rates (0.03 to 0.05 h^?1) but residual starch was present at higher dilution rates and CGT synthesis was repressed. Enzyme titres obtained in chemostat cultures at D = 0.03 h^?1 using defined medium containing 13 g starch/1 were 2.75 times greater than the maximum obtainable by batch cultivation and about 20 times greater than those reported by other workers using medium containing diced potato and CaCO₃. A two-stage chemostat cultivation was performed using dilution rates of 0.1 h^?1 and 0.033 h^?1 in the first and second stages, respectively. The CGT activity in the second stage increased by 57 per cent when a maintenance feed of starch was supplied at 0.08 g g^?1 dry biomass h^?1. Only negligible CGT titres were obtained when a dilution rate of 0.5 h^?1 was used in the first stage. For reasons not understood, DM medium would not support biomass yields greater than 5 g 1^?1. This limitation was not due to production of an inhibitor, or to deficiency of N, Fe, Zn, Mn, thiamine or biotin.     

Continuous Toluene Vapor Remediation in a Well‐Mixed Bioreactor

Mass transfer and bioremediation of toluene from a contaminated air stream has been investigated using a continuous flow, stirred tank bioreactor. The toluene mass transfer coefficients varied from 3.1 to 3.8 h⁻¹ as the agitation speed increased from 300 to 600 rpm. Using a pure culture, toluene could not be continuously bioremediated as a sole substrate. When ethanol was used as a cosubstrate, toluene was continuously captured and bioremediated at rates up to 90 mg/L·h with removal efficiencies up to 90%, while ethanol was simultaneously degraded at rates up to 250 mg/L·h. Using benzyl alcohol as the cosubstrate, toluene removal efficiencies were above 97% at continuous loading rates of 90 mg/L·h and benzyl alcohol loading rates up to 300 mg/L·h.     

应用Coriolus versicolor催化染料及印染废水脱色

利用固定化C .versicolor菌丝球对 4种染料和印染废水的脱色进行了研究 .在三角瓶中采用重复分批加料方式对酸性橙溶液脱色至少可以进行 10批 ,每批在 2 4h内完成 97%以上的脱色效果 .菌丝球对其他 3种染料也有较好的脱色效果 .在脱色过程中添加碳源是必要的 .此外 ,还利用自制的气升式反应器对酸性橙和印染废水的连续降解进行了研究 .当稀释率为 0 .0 0 5 6h^-1、通风量为 1.1L·min^-1时 ,酸性橙溶液的脱色率可达 97%;当稀释率为 0 .0 14h^-1、通风量为 1.4L·min^-1时 ,印染废水的脱色率为 93.5 %,连续操作 5d后 ,菌丝球的脱色能力没有下降 .     

Photoautotrophic cultivation of the green alga Chlamydomonas reinhardtii as a method for carbon dioxide fixation and α-linolenic acid production

Focusing on CO₂ fixation and α-linolenic acid (ALA) production, photoautotrophic cultivation of the green alga Chlamydomonas reinhardtii was investigated by using a culture medium of pH 6.8 under a 5 vol% CO₂-enriched atmosphere. The optimum cultivation temperature and light intensity for growth were 25°C and 12 klux, respectively. The cellular ALA content nearly doubled to 11.9 mg/g of dry cells when the concentration of culture medium was doubled. Simulation of chemostat cultivation showed that the rate of CO₂ fixation and ALA productivity per unit volume of culture medium could reach 1.01 kg CO₂/(m³ · d) and 7.46 g ALA/(m³ · d), respectively, at a cell concentration of 0.57 kg cells/m³.     

The effects of dilution rate and glucose concentration on continuous acetone–butanol–ethanol fermentation by Clostridium acetobutylicum immobilized on bricks

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of butanol through biological routes has attracted increasing attention. However, low butanol productivity severely impedes its potential industrial production. It is known that the immobilization of whole cells can enhance productivity in the acetone‐butanol‐ethanol (ABE) continuous fermentation process. Therefore, the objective of this study was to develop a low‐cost continuous operation for butanol production. RESULTS: Bricks were chosen as cell support because of their low cost and ease of use for immobilization. The solvent productivity for the bricks with immobilized cells was 0.7 g L^?1 h^?1, 1.89 times that of free cells (0.37 g L^?1 h^?1) at a dilution rate of 0.054 h^?1. The productivity improvement can contribute to greater retention of biomass inside the reactor due to immobilization. The increase in glucose feed concentration raised total solvent production. However, it resulted in a decrease in yield (grams of solvents produced per gram of glucose introduced). Continuous operation with immobilized cells at a dilution rate of 0.107 h^?1 resulted in a solvent productivity of 1.21 g L^?1 h^?1, 2.1 times that of the operation at 0.027 h^?1. However, the yield (butanol produced per glucose consumed) was decreased to 0.19 from 0.29 under the same glucose feeding condition of 60 g L^?1. CONCLUSION: The increase in dilution rate and feed glucose concentration enhanced productivity, but decreased the utilization of substrates and the final solvent concentration. Therefore, a balance between productivity and glucose utilization is required to ensure continuous process operation. Copyright © 2011 Society of Chemical Industry     

Removal of nitrogen in wastewater by polyvinyl alcohol (PVA)-immobilization of effective microorganisms

To remove nitrogen and carbon simultaneously from municipal wastewater, a mixture of effective microorganisms (EM) was immobilized in polyvinyl alcohol (PVA) hydrogel beads. The modified PVA beads with calcium alginate show characteristic pores and mechanical stability and flexibility. The EM-immobilized PVA system was established in a 3 L sequential batch reactor (SBR) with a synthetic wastewater and operated at an HRT of 12 h with COD loading rate of 0.5–2.4 g COD/L·d. In this system, intermittent aeration is more efficient than continuous aeration, and removal rates of COD and total nitrogen (T-N) were increased as the feed COD/N ratio was increased from 1.9 to 5.6. At an optimal condition, 73% of total nitrogen and 93% of COD were stably removed at a COD loading rate lower than 2.4 g COD/L·d and at 3: 1 ratio of aerobic time to anoxic time.