利用甘蔗糖蜜与乳清粉厌氧发酵制备丁二酸

考察了甘蔗糖蜜替代昂贵葡萄糖作为碳源、乳清粉替代大部分酵母粉作为氮源时,对Actinobacillus succinogenes NJ113发酵制备丁二酸的影响。血清瓶厌氧发酵结果证明：对照组（葡萄糖40 g/L）的丁二酸产量仅为26.04 g/L,而以糖蜜为碳源（以总还原糖计算为40 g/L）时,丁二酸产量达到28.27 g/L,比对照组提高了8.57%。在此基础上,以糖蜜为碳源、不同比例的乳清粉和酵母粉为混合氮源发酵制备丁二酸,确定了糖蜜、乳清粉和酵母粉混合使用的最佳浓度分别为40 g/L、8 g/L和2 g/L。此外,在3 L发酵罐体系中添加40 g/L糖蜜、8 g/L乳清粉、2 g/L酵母粉进行发酵试验,实验结果证明：丁二酸终产量达到32.54 g/L,收率达到81.13%。     

A.Succinogenes甘油利用突变株对丁二酸合成的影响

以葡萄糖为碳源利用A.succinogenes NJ113生产丁二酸时,副产物乙酸较高,以A.succinogenes NJ113为出发菌,采用自主设计的连续培养装置,筛选利用甘油能力较强的突变株,最终筛选到一株能够利用浓度达到8 g/L的突变株ZH99。此突变株在以27 g/L的葡萄糖和3 g/L的甘油作为碳源,在血清瓶中厌氧发酵,丁二酸产量达到20.81g/L,比原始菌株的丁二酸的量20.42 g/L稍有提高,同时,乙酸的浓度仅为5.02 g/L,比对照组(仅以葡萄糖为碳源)降低了38.25%,效果显著。     

Actinobacillus succinogenes NJ113产丁二酸过程中的底物抑制

研究了分批发酵条件下以葡萄糖作为底物对产琥珀酸放线杆菌Actinobacillus succinogene NJ113发酵产丁二酸的影响,针对底物抑制现象,采用变速补料控制发酵罐中葡萄糖浓度的补料分批发酵方式.结果表明,发酵过程中将葡萄糖浓度控制在0～10g/L,以Na2CO3作为pH调节剂,经26h厌氧发酵,消耗60g/L葡萄糖,能积累45.27g/L丁二酸,得率达75.45%,生产强度为1.74g/(L·h),比初始葡萄糖浓度为60g/L的分批发酵周期缩短了18.75%,主产物丁二酸的得率和生产强度分别提高了5.44%和31.82%,副产物甲酸产量有所减少,而乙酸产量有所增加.通过代谢网络中相关酶的酶活分析,解析了补料过程中主副产物的分布.     

产琥珀酸放线杆菌固定CO_2制备丁二酸

在富含CO2的厌氧环境下,产琥珀酸放线杆菌NJ113固定CO2合成丁二酸作为主要代谢终产物。在5 L发酵罐探讨了培养条件对产琥珀酸放线杆菌NJ113固定CO2制备丁二酸的影响。考察了CO2供体形式、通气量、搅拌转速、培养温度和pH值对产琥珀酸放线杆菌NJ113厌氧发酵过程中CO2固定速率以及丁二酸产率的影响。结果表明,选择CO2气体作为CO2供体,CO2通气量为0.75 L/min,搅拌转速达到200 r/min,培养温度为37℃,NaOH调节pH值为6.6,可增加细胞内可利用的CO2。在此优化条件下培养,CO2固定速率达到0.6 g/(L.h),丁二酸产率达到1.61 g/(L.h)。     

多纤维素酶协同降解玉米秸秆及水解液微生物油脂发酵研究

以富含纤维二糖酶的黑曲霉酶曲协同降解纤维素水解液,利用油脂微生物转化纤维素水解液生产微生物油脂.研究结果表明,酶曲中的纤维二糖酶可以将纤维素水解液中存在的纤维二糖进一步水解成葡萄糖,而油脂酵母Cryptococus curuatus03又能将葡萄糖迅速转化成微生物油脂储存在体内.cryptococcus curvatus 03利用纤维素水解液(总还原糖质量浓度为31.5 g/L).经过4次补糖,细胞生物量为49.3 g/L,油脂含量达到60.1%质量分数.     

大豆渣制备细菌纤维素的研究

细菌纤维素(BC)是一类由微生物产生的纳米纤维素,其偏高的生产成本,尤其是成本相对较高的发酵碳源,限制了其工业化生产和应用。以廉价丰富的大豆渣为原料,进行稀酸预处理,剩余的不溶性滤渣经纤维素酶的水解获得可发酵糖。分别以酸预处理液和酶水解液配制培养基,用来制备细菌纤维素。结果表明:以酶解液作为发酵碳源的BC产量明显高于以酸预处理液为碳源时的产量;且以Ca(OH)2处理的酶解液为碳源时,BC产量可达5.52 g/L,远高于葡萄糖对照组(7.4倍),表明大豆渣作为碳源生产BC具有良好的应用前景和商业价值。     

纤维素水解液中抑制剂对纤维二糖利用菌株发酵能力的影响

木质纤维素在预处理的过程中会产生呋喃类、酚类和弱酸类物质,抑制菌株的生长和发酵。研究了典型抑制剂糠醛、苯酚和乙酸对可利用纤维二糖的工程酿酒酵母菌株生长和发酵的影响,考查了分别以纤维二糖和葡萄糖作为单一碳源时菌株对抑制剂的耐受能力。结果发现,糠醛对菌株的纤维二糖和葡萄糖利用能力的抑制作用随糠醛浓度增加而增大。低浓度(≤0.5 g/L)的苯酚对纤维二糖利用有一定的促进作用,高浓度(1.5 g/L)的苯酚会抑制菌株的生长和发酵。乙酸对菌株纤维二糖利用的影响最为显著,可以明显抑制菌株的生长、纤维二糖利用和乙醇生产,而一定浓度(0.5~4.0 g/L)的乙酸会促进葡萄糖的利用。研究中还发现,复合抑制剂对纤维二糖利用菌株的抑制作用强于单一抑制剂。     

纤维素水解液中木糖发酵制丁醇

对实验室菌种进行筛选后,得到一株能利用纤维素水解液木糖发酵生产丁醇的菌株。研究发现,该菌株不仅能利用水解液中的葡萄糖,还可以利用水解液中的木糖。对菌种生长特性探索,批式发酵中碳源、氮源以及CaCO3等条件优化后,得到最佳种子培养时间为20～24 h,并确定了木糖浓度为20 g/L的纤维素水解液用于15 L发酵罐实验,在37 ℃静置培养84 h,丁醇产量10.95 g/L,总溶剂16.78 g/L（丙酮、乙醇、丁醇三者之和）,木糖利用率达到70%以上,总溶剂转化率为39.4%。解决了纤维素水解液中木糖不能被利用而造成的经济损失问题。     

豆粕水解液为氮源细菌厌氧流加发酵生产L-乳酸

采用细菌厌氧发酵法生产L-乳酸,由实验确定了最佳接种量、发酵温度和pH调节剂,考察了初始葡萄糖浓度对L-乳酸生产的影响,确定初始糖浓度为70~90 g/L时得率、产率、最终生物量分别达到92.68 g/g, 3.17 g/(L×h)和8.5′107 mL-1. 为进一步降低L-乳酸生产成本,以豆粕水解液为氮源代替酵母粉,同时应用流加发酵技术,L-乳酸产量、得率、产率及转化率分别达到155 g/L, 95.5 g/g, 1.64 g/(L×h)和96.9%. 在保证L-乳酸最终浓度的同时可降低生产成本,为进一步工业化奠定了基础.     

响应面优化木糖母液发酵产丁二酸

对产琥珀酸放线杆菌（Actinobacillus succinogenes）GXAS137发酵木糖母液产丁二酸的条件进行优化,探索利用废弃木糖母液合成高附加值丁二酸的可行性。首先通过Plackett-Burman实验设计确定影响丁二酸发酵的显著因子,然后采用最陡爬坡实验逼近各显著因子的最优区域,最后通过Box-Behnken实验设计确定各因子的最优水平。影响木糖母液发酵产丁二酸的显著因子及最优浓度分别为：木糖母液64.75g/L,玉米浆15.71g/L,碱式碳酸镁46.39g/L。在最优发酵培养条件下,丁二酸产量达到38.01g/L,比优化前提高了20.7%,与模型预测值（38.41g/L）基本一致。进一步利用2L发酵罐进行了放大试验,发酵72h丁二酸产量最高可达48.99g/L,较厌氧瓶发酵提高了28.9%,丁二酸得率为0.80g/g总糖。结果表明,采用低价的木糖母液作为底物,可为未来低成本、高效产业化生产丁二酸奠定坚实的基础。     

Comparison of bacterial cellulose production by Gluconacetobacter xylinus on bagasse acid and enzymatic hydrolysates

To fulfill the comprehensive utilization of cellulose and hemicellulose components in bagasse for bacterial cellulose (BC) production, both bagasse acid and enzymatic hydrolysates were used for BC production by Gluconacetobacter xylinus. Although the BC accumulation rate was slower during the early period of fermentation in the bagasse acid hydrolysate than in the enzymatic hydrolysate, the highest BC yield (1.09 vs. 0.42 g/L) was higher in the bagasse acid hydrolysate. The substrate utilization was evaluated in both bagasse acid and enzymatic hydrolysates, and glucose, xylose, and acetic acid were better carbon sources than arabinose and cellobiose for G. xylinus. The structure of the BC samples obtained from bagasse acid and enzymatic hydrolysates, including the microscopic morphology, functional groups, and crystals, was similar especially in the later phase of fermentation, which was analyzed by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. Thus, both bagasse acid and enzymatic hydrolysates could be promising substrates for BC production. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45066.     

在内置式植物纤维床反应器中用糖蜜固定化发酵制丙酸

开发了一种综合利用制糖工业副产物生产丙酸的新方法,将制糖工业副产物甘蔗渣和糖蜜分别作为固定化载体和碳源,应用于丙酸生产.以甘蔗渣为固定化载体构建了一种内置式植物纤维床反应器(Inner plant fibrous-bed bioreactor,IPFB).以Propionibacterium freudenreichii CCTCC M207015为发酵菌株,对在IPFB中分别用未处理糖蜜及糖蜜水解液为碳原发酵制丙酸进行考察.以未处理糖蜜为碳源发酵,254 h丙酸浓度为52.39 g·L~(-1),丙酸生产速率为0.21 g·(L·h)~(-1);糖蜜水解液为碳源发酵,254 h后丙酸浓度达75.18 g·L~(-1),丙酸生产速率达0.30 g·(L·h)~(-1),丙酸占总有机酸比例达83.10%(w/w).稳定性实验表明以糖蜜水解液为碳源,利用IPFB发酵生产丙酸10批仍然保持较高的丙酸生产效率.扫描电镜显示大量丙酸杆菌的细胞吸附于甘蔗渣表面与间隙中,有效实现了高密度发酵.     

利用甘蔗糖蜜半连续发酵生产琥珀酸

为获得较高的琥珀酸发酵产量和生产强度,对Actinobacillus succinogenes CGMCC1593两级双流半连续发酵甘蔗糖蜜生产琥珀酸的工艺过程进行了研究。通过对一级罐初始总糖浓度、补加培养基体积分数和批次发酵时间等发酵条件的优化,琥珀酸产量较分批发酵36 h提高12.9％,与补料分批发酵结果接近;生产强度较分批发酵和补料分批发酵分别提高111％和114%。     

Effects of three main sugars in cane molasses on the production of butyric acid with <Emphasis Type="Italic">Clostridium tyrobutyricum</Emphasis>

The effects of three main sugars in cane molasses were investigated systematically to prepare a cost-effective medium for butyric acid bioproduction. Additionally, 30 g/L corn steep liquor was screened out as the suitable nitrogen source. In the batch fermentation of free cells, when 60 g/L glucose was the only carbon source, 21.28 g/L butyric acid was achieved after 30 h cultivation. Similar product concentration, productivity and yield were obtained when 60 g/L fructose was applied. The utilization of sucrose would bring about lower productivity (0.29 g/L·h) and product concentration (18.15 g/L), but the yield of butyric acid/sucrose (0.34 g/g) is almost the same as that from glucose or fructose (0.35 g/g). Finally, the sugar mixture (15 g/L glucose, 20 g/L fructose and 35 g/L sucrose) was employed to produce butyric acid in a fibrous-bed bioreactor (FBB), and 40.11 g/L butyric acid was produced with one simple fed-batch strategy.     

基于pH恒定补糖的生物基丁二酸高效合成

通过确定大肠杆菌在产酸阶段葡萄糖的消耗与酸中和剂碳酸钠间的定量关系,建立了pH恒定补糖策略,能够使发酵液中葡萄糖浓度维持在稳定水平。与分批发酵相比,采用pH恒定补糖且维持葡萄糖浓度在较低的水平对丁二酸的积累是有利的。当采用pH恒定补糖并控制葡萄糖质量浓度在10g/L时,丁二酸最终质量浓度达到57.6 g/L,生产效率达到1.15 g/(L·h)。     

利用改性载体固定化大肠杆菌产琥珀酸

采用聚乙烯亚胺（PEI）和戊二醛（GA）对棉纤维进行化学修饰,考察了载体改性后的性能和对固定化大肠杆菌产丁二酸的影响。改性后的载体菌体负载量提高了63.3%。培养基中葡萄糖浓度为43 g/L,添加改性棉纤维120g/L,以MgCO3为缓冲盐,进行批式发酵,丁二酸浓度达到29.6 g/L,比未改性棉纤维提高了11.3%;丁二酸收率达到70.5%,比改性前提高了7.5%;丁二酸生产速率达到0.66 g/(L?h), 比改性前提高了37.5% 。对该材料固载的细胞进行7次重复批式发酵,丁二酸产量、转化率和产率没有下降趋势,具有一定的重复稳定性。     

Bioconversion of corn stover hydrolysate to ethanol by a recombinant yeast strain

Three corn stover hydrolysates, enzymatic hydrolysates prepared from acid and alkaline pretreatments separately and hemicellulosic hydrolysate prepared from acid pretreatment, were evaluated in composition and fermentability. For enzymatic hydrolysate from alkaline pretreatment, ethanol yield on fermentable sugars and fermentation efficiency reached highest among the three hydrolysates; meanwhile, ethanol yield on dry corn stover reached 0.175 g/g, higher than the sum of those of two hydrolysates from acid pretreatment. Fermentation process of the enzymatic hydrolysate from alkaline pretreatment was further investigated using free and immobilized cells of recombinant Saccharomyces cerevisiae ZU-10. Concentrated hydrolysate containing 66.9 g/L glucose and 32.1 g/L xylose was utilized. In the fermentation with free cells, 41.2 g/L ethanol was obtained within 72 h with an ethanol yield on fermentable sugars of 0.416 g/g. Immobilized cells greatly enhanced the ethanol productivity, while the ethanol yield on fermentable sugars of 0.411 g/g could still be reached. Repeated batch fermentation with immobilized cells was further attempted up to six batches. The ethanol yield on fermentable sugars maintained above 0.403 g/g with all glucose and more than 92.83% xylose utilized in each batch. These results demonstrate the feasibility and efficiency of ethanol production from corn stover hydrolysates.