嗜鞣管囊酵母发酵柑橘皮水解液生产乙醇的研究

本文旨在研究嗜鞣管囊酵母利用柑橘皮半纤维素水解液发酵生产乙醇的可行性.采用木聚糖酶水解柑橘皮半纤维素,利用嗜鞣管囊酵母(Pachysolen tannophilus)进行木糖发酵生产乙醇;测定嗜鞣管囊酵母细胞生长曲线,乙醇生产及木糖残留曲线,并研究发酵工艺条件.试验结果表明,嗜鞣管囊酵母可有效利用柑橘皮水解液中的木糖进行细胞生长和乙醇生产.以柑橘皮水解液为碳源,发酵生产乙醇是可行的.优化的乙醇发酵生产工艺条件是:发酵时间20 h、温度28℃、摇床转速100 r/min、初始pH 4.5、接种量5％.在此工艺条件下,乙醇产量10.1 mg/mL,乙醇得率0.388 g乙醇/g木糖,是理论得率的84.3％.     

酵母发酵条件的优化及其发酵造纸污泥产乙醇

优化了酿酒酵母Saccharomyces cerevisiae GIM-2发酵工艺条件并对其发酵造纸污泥产乙醇进行了研究。以模拟造纸污泥水解液中糖成分的混合糖为试验原料,采用响应面分析法优化酵母发酵生产乙醇工艺,得优化条件:温度33.1℃,pH值5.4,摇床转速50r/min,发酵24h糖醇转化率为38%。造纸污泥在纤维素酶作用下水解48h,纤维素转化率为58.2%,水解液在优化条件下发酵24h糖醇转化率为28.4%,产率达0.14g乙醇/g污泥,是理论值的37.3%。     

管囊酵母发酵生产乙醇的实验研究

嗜鞣管囊酵母(Pachysolen tannophilus)As 2.1585可以直接发酵木糖产乙醇.研究了供氧水平、培养基初始pH值、接种量等条件对嗜鞣管囊酵母As 2.1585发酵产乙醇的条件.结果表明,在温度28℃、转速100 r/min条件下,嗜鞣管囊酵母发酵木糖产乙醇适宜在高好氧条件下进行,产乙醇的最适初始pH值为5.0,最适接种浓度2%,当水解液木糖浓度为3 g/100 mL时,最大乙醇浓度为0.8 g/100 mL,是理论得率的85%.     

蒸汽爆破尾叶桉木材纤维素酶水解液发酵单细胞蛋白

用高效液相色谱对蒸汽爆破尾叶桉木材的纤维素酶水解液进行了还原糖和乙酸含量分析,通过酿酒酵母和假丝酵母混合接种,对水解液进行了摇瓶发酵单细胞蛋白的工艺研究,确定了发酵的最佳工艺条件。结果表明,水解液中主要含有葡萄糖和木糖,用双菌种混合发酵单细胞蛋白的最佳发酵条件为:酿酒酵母(Sacchromyces cerevisive):假丝酵母(Candida utilis2.587)为1:3,发酵温度31℃,初始pH4.5,初始还原糖浓度17～18g/L,发酵时间27h。     

土壤中产木糖醇酵母菌株的筛选其发酵条件优化

本文以木糖为唯一碳源从土壤中筛选得到可以耐受高浓度木糖的菌株,再经过复筛选出一株高产木糖醇的酵母菌株Y-9。经高效液相色谱(HPLC)和红外扫描分析,确定菌株Y-9发酵利用木糖转化得到的主要产物为木糖醇。通过单因素实验、正交试验等手段,对菌株Y-9发酵产木糖醇的培养基组分和发酵条件进行了优化,进一步提高了目的菌株的木糖醇产率和转化率,确定了菌株Y-9摇瓶发酵木糖转化木糖醇的最优培养基和发酵条件。在木糖初始浓度为200 g/L,氮源为酵母膏3.0 g/L,硫酸铵2.0 g/L,玉米浆10.0 mL/L,硫酸镁0.1 g/L,初始pH为6.0,转速为180 r/min,接种量为4%的条件下,菌株Y-9的木糖醇产率为160 g/L左右,木糖醇生成速率为1.67 g/L.h,木糖/木糖醇转化率达到80%以上,是一株具有良好工业化研究开发价值的木糖醇生产菌株。     

小型发酵罐条件下树干毕赤酵母木糖发酵条件优化

以树干毕赤酵母m4为发酵木糖菌株,研究了5L发酵罐中不同培养条件对酵母发酵木糖生成乙醇和酵母生长规律的影响。结果表明,5L发酵罐中最佳发酵条件为:初始木糖浓度108g/L,温度28℃,通气量30L/h,转速300r/min,接种量12.5%,最适pH值为4.8,此时木糖转化率、乙醇得率最高,分别为98.5%,0.47g/g,乙醇产量有较大提高,50.0g/L。     

法夫酵母产新科斯糖的发酵条件

通过单因素实验及正交试验对法夫酵母摇床发酵产新科斯糖的培养基组成和培养条件进行优化,得出该菌株产新科斯糖的最佳发酵条件为:蔗糖110g/L,玉米浆粉8g/L,种龄48h,接种体积分数10%,发酵周期24h,初始pH6.5,摇床转速220r/min,发酵温度18℃。经优化后新科斯糖产量最高可达73.2g/L,蔗糖利用率为66.5%,比优化前发酵效率提高了87.1%。     

酿酒酵母Y3401产乙醇条件优化及其产香特性

以酿酒酵母Y3401为出发菌株,对其产乙醇条件进行优化,并探究其发酵产香特性。在乙醇发酵培养基的基础上,采用单因素Step-by-step和正交试验方法确定酿酒酵母Y3401高产乙醇的发酵条件是:葡萄糖300 g/L,酵母浸粉37.8 g/L,初始pH 5.2,活化24 h,接种量3%,装液量30 mL/250 mL,在30℃,100 r/min条件下培养32 h。在此条件下,酵母Y3401产乙醇质量浓度高达117.2 g/L,相比初期产量(52.4 g/L)提高了1.24倍。采用顶空固相微萃取-气质联用仪分析该酵母的高粱浸出液在30℃,100 r/min培养32 h后的挥发性风味物质,结果表明,该酵母能产苯乙醇、乙酸乙酯、乙酸苯乙酯等40种对白酒品质有重要贡献的风味物质。这说明酿酒酵母Y3401不仅高产乙醇,而且产生多种改善白酒品质的风味物质,这些特性有利于其在白酒酿造中的应用。     

玉米秸秆水解液生产燃料酒精的研究

通过对稀硫酸预处理玉米秸秆水解液发酵生产燃料酒精各因素进行分析，初步确定了利用奥默毕赤氏酵母的最适发酵条件：发酵温度为36℃，时间为60h，通风量为0．081／min,初始还原糖浓度为74．0g／1。在最适发酵条件下，乙醇产率为0．327g／g。在73．96g／1的水解液中添加20g／1葡萄糖会导致酵母发酵过程出现“二次生长”现象。     

产α-葡萄糖苷酶抑制剂菌株的筛选及发酵条件优化

从农田土壤中筛选得到一株产α-葡萄糖苷酶抑制剂能力较强的UN-8菌株,菌株对其发酵条件进行初步优化,得到最优条件为玉米粉3g/100mL、酵母膏1.2g/100mL、溶氧量30mL/250mL、摇床转速160r/min、发酵时间3d、初始pH8.0以及培养温度32℃。在此条件下,α-葡萄糖苷酶抑制剂的抑制率为75.34%,比初始抑制率(60.79%)提高了14.55%。     

固定化热带假丝酵母发酵氨浸稻秸水解液生产木糖醇

采用海藻酸钙固定化热带假丝酵母细胞发酵氨水浸泡稻秸半纤维素水解液生产木糖醇。为了提高木糖醇的转化率,对发酵条件进行了研究。发酵在250 mL锥形瓶中进行。向水解液中补充适量氮源和营养盐等营养物质提高了木糖醇的生产速率,但木糖醇转化率没有因此而提高。适宜的初始pH和细胞干浓度分别为4-5和1.22 g/L。在这些条件下,进行了固定化细胞重复法较高浓缩度水解液的试验。结果发现,固定化细胞能在初始木糖浓度为104.2 g/L的水解液中重复批式发酵5次,木糖醇平均得率和生产速率分别为0.737 g/g和0.533 g/(L.h)。     

Xylitol production from rice straw hemicellulose hydrolyzate by polyacrylic hydrogel thin films with immobilized Candida subtropicalis WF79

Xylose from rice straw hemicellulose hydrolysate was fermented for xylitol production using Candida subtropicalis WF79 cells immobilized in polyacrylic hydrogel thin films of 200 mum thickness. Cell immobilization was conducted by first suspending the yeast cells in a mixture of 2-hydroxyethyl methacrylate (HEMA, hydrophilic monomer), polyethylene glycol diacrylate (PEG-DA, crosslinking agent), and benzoin isopropyl ether (photoinitiator). The mixture was then allowed to form polyacrylic hydrogel thin films, between two pieces of glass sheets, by UV-initiated photopolymerization. The hemicellulose of rice straw was hydrolyzed using dilute sulfuric acid at 126 degrees C. The hydrolysate was neutralized with calcium hydroxide. After separating the solid residues and calcium sulfate precipitates by filtration, the hydrolysate was treated with charcoal to partially remove potential inhibitory substances, followed by vacuum concentration to obtain solutions of desired xylose concentrations for yeast fermentation. The thin films with immobilized yeast cells were submerged in the xylose solution from rice straw hydrolysate for fermentation in an Erlenmeyer flask. The maximum yield was 0.73 g of xylitol per gram of xylose consumed. In the 52.5-day long durability test, after 40 d of repeated batchwise operation, the fermentation activities of the cell immobilized in thin films began to decline to a yield of 0.57 g/g at the end.     

固定化增殖细胞发酵半纤维素糖类的研究

采用海藻酸钠包埋及进一步增殖培养，将休哈塔假丝酵母（ＣａｎｄｉｄａｓｈｅｈａｔａｅＲ）的细胞密集固定在凝胶珠表层，大大减小了传递阻力，为该菌的“半好气”发酵创造了有利条件。试验结果表明，ＣａＣｌ２浓度以２％为宜，凝胶中掺入适量的Ａｌ２Ｏ３（１．２％）能明显增加凝胶珠的机械强度及使用寿命。固定化增殖细胞能够利用己糖和戊糖及８０ｇ／ｌ的混合糖（己糖与戊糖各占一半）。经１２ｈ发酵，糖的利用率达９０．５％（相同条件下的游离细胞发酵需４８ｈ）。混合糖发酵的适宜条件为：温度３４～３６℃；初始糖浓度８０ｇ／Ｌ；通气量３．３ｍｌ／ｍｌ发酵体积·ｈ。固定化休哈塔假丝酵母能成功地发酵玉米秆水解液、杨木水解液及亚硫酸盐制浆废液，酒精得率达理论值的９０％以上，具有广阔的实际应用前景。     

THE ENHANCEMENT OF AMMONIA PRETREATMENT ON THE FERMENTATION OF RICE STRAW HYDROLYSATE TO XYLITOL

In xylitol fermentation from rice straw hydrolysate by Candida tropicalis As2.1776, ammonia steeping was employed to pretreat the rice straw. Experimental results showed that the content of toxic compounds created in the hydrolysis process, such as acetic acid and phenolic compounds, was greatly reduced and the fermentation of the hydrolysate was enhanced. Xylitol fermentation was investigated in flasks and a 2‐L bioreactor, respectively. The xylitol yield factor and volumetric productivity were 0.746 g/g and 0.686 g/(L·h) in the lab‐flask fermentation, respectively. The corresponding results conducted in bioreactor fermentation were 0.689 g/g and 0.697 g/(L·h), respectively.     

Reusable Floating Beads with Immobilized Xylose-Fermenting Yeast Cells for Simultaneous Saccharification and Fermentation of Lime-Pretreated Rice Straw

Novel bioreactor beads for simultaneous saccharification and fermentation (SSF) of lime-pretreated rice straw (RS) into ethanol were prepared. Genetically modified Saccharomyces cerevisiae cells expressing genes encoding xylose reductase, xylitol dehydrogenase, and xylulokinase were immobilized in calcium alginate beads containing inorganic lightweight filler particles to reduce specific gravity. For SSF experiments, the beads were floated in slurry composed of lime-pretreated RS and enzymes and incubated under CO₂ atmosphere to reduce the pH for saccharification and fermentation. Following this reaction, beads were readily picked up from the upper part of the slurry and were directly transferred to the next vessel with slurry. After 240 h of incubation, ethanol production by the beads was equivalent to that by free cells, a trend that was repeated in nine additional runs, with slightly improved ethanol yields. Slurry with pre-saccharified lime-pretreated RS was subjected to SSF with floating beads for 168 h. Although higher cell concentrations in beads resulted in more rapid initial ethanol production rates, with negligible diauxic behavior for glucose and xylose utilization, no improvement in the ethanol yield was observed. A fermentor-scale SSF experiment with floating beads was successfully performed twice, with repeated use of the beads, resulting in the production of 40.0 and 39.7 g/L ethanol. There was no decomposition of the beads during agitation at 60 rpm. Thus, this bioreactor enables reuse of yeast cells for efficient ethanol production by SSF of lignocellulosic feedstock, without the need for instruments for centrifugation or filtration of whole slurry.     

竹笋壳水解液中生物转化木糖醇发酵条件优化

该研究以热带假丝酵母（Candida tropicalis）为出发菌株,以竹笋壳水解液为木糖来源,进行木糖醇生物转化。对木糖发酵工艺中的起始pH、发酵温度、装液量、接种量及转速进行优化,确定最佳条件。结果表明,在起始pH 6.0、发酵温度35 ℃、装液量60 mL/250 mL、接种量8%和转速160 r/min条件下,木糖醇质量浓度为（10.8±0.2） mg/mL,转化率达到（61.5±2.5）%。     

驯化和胶囊包裹的假丝酵母LF04发酵玉米芯水解液生产木糖醇(英文)

玉米芯的酸水解液是木糖醇生产的重要原料,但是该水解液中含有糠醛、酚类等对后续微生物发酵有毒害作用的化合物。本研究从土壤中分离了一株似假丝酵母LF01,通过驯化和微胶囊包裹来提高其对水解液的抗性。结果表明通过多次驯化并进行包裹的假丝酵母LF04能在玉米芯水解液中不经任何脱毒处理发酵木糖生产木糖醇。在pH5.5 溶氧为 0.15vvm 的条件下发酵 88h,木糖转化率为 76%,木糖醇浓度达 61.768g/L。远高于其出发菌株。该结果表明采用该方法有望用于木糖醇的工业化生产。     

用玉米芯水解液发酵木糖醇的研究

对用玉米芯水解液发酵木糖醇进行了研究。结果表明玉米芯水解液中的葡萄糖和杂质成分对木糖醇发酵具有抑制作用。试验显示一些添加剂能明显减轻这种抑制作用。本试验用玉米芯水解液进行的木糖醇发酵中,木糖醇的转化率为理论值的74.9%。     

不依赖IPTG诱导产木糖醇大肠杆菌工程菌的构建

该研究采用分子生物学技术构建不依赖异丙基-β-D-硫代半乳糖苷（IPTG）诱导产木糖醇的大肠杆菌（Escherichia coli）工程菌,并研究启动子、质粒拷贝数、诱导剂IPTG的添加、基因xylA和xylB的敲除以及木糖含量对工程菌发酵产木糖醇的影响。结果表明,当转速为200 r/min时,E. coli AI07/pWYZ-1（启动子为lacP）的木糖醇产量是E. coli AI07/pAGI02（启动子为pflB-p6）的1.8倍;E. coli AI07/pWYZ-2（中拷贝质粒pBR322）的木糖醇产量高于E. coli AI07/pWYZ-1（高拷贝质粒pUC19）,分别为19.56 g/L、7.90 g/L;是否添加诱导剂IPTG对E. coli AI07/pWYZ-2产木糖醇影响不大,且在发酵96 h时,木糖醇产量极显著高于E. coli AI05/pWYZ-2（P＜0.01）,其在不添加IPTG的条件下,当木糖初始质量浓度为80 g/L,发酵时间为108 h时,木糖醇产量达48.7 g/L。     

红曲液态发酵高产色素低产桔霉素的工艺条件

通过优化液态发酵过程及提取精制过程中的相应措施,可有效降低红曲桔霉素含量。优化后的小型发酵罐主要工艺条件是:精选氮源(大豆水解液为佳);合理的通风量和搅拌转速[小型罐通风强度1.0L/(L·min),转速200r/min];在较高的温度下发酵(36℃);尽可能缩短发酵时间(96h);成熟发酵液在过滤前调节pH,使色素沉淀,从而与桔霉素分离。所得到红曲红色价分别为2 000U/g、10 000 U/g,桔霉素含量分别为0.282 mg/kg和1.373 mg/kg(折算为500U/g时的桔霉素含量为0.075mg/kg和0.067mg/kg),均低于红曲色素日本标准中桔霉素含量的限量指标(0.2 mg/kg即500 U/g)。说明通过发酵工艺及提取精制的优化,在不影响色素高产的情况下可将红曲色素中的桔霉素含量降至理想的水平。