米根霉乳酸发酵的研究进展

乳酸主要通过发酵生产，米根霉乳酸发酵过程中的代谢途径是EMP途径和TCA途径，菌体形态的控制对产量有很大的影响。介绍了发酵工艺研究进展，并且分析了代谢工程原理在米根霉乳酸发酵中的应用。     

固定化米根霉发酵生产有机酸的现状及发展趋势

米根霉是生产绿色平台生物化学品L一乳酸、富马酸等有机酸的理想菌种.游离的米根霉发酵生产有机酸时存在菌种利用率低、生产效率低等一系列问题,菌体固定化发酵研究旨在克服这些困难.目前米根霉固定化发酵生产有机酸技术的研究主要集中于载体固定化技术的研究,然而无载体固定化技术作为一种全新的细胞固定化技术正在迅速的发展与完善.本文对固定化米根霉发酵生产有机酸的研究现状以及未来发展趋势进行了综合评述与分析.     

固定化米根霉发酵生产乳酸的研究进展

根霉属中的米根霉是迄今认为生产L-乳酸较为理想的菌种.利用游离的米根霉发酵乳酸时会产生菌种利用率低、生产效率低等一系列不足,因此展开了菌体固定化发酵的研究.目前米根霉固定化发酵工程的研究主要集中于载体的选择和新型生物反应器的研制.本文对此研究进展作了综合评述与讨论,认为米根霉固定化发酵乳酸可以进一步降低生产成本,提高乳酸产率.     

转盘反应器固定米根霉的L－乳酸发酵

研究了米根霉的固定化方法，研制了用吸附法固定米根霉的生物转盘反应器，考察了在该反应器中培养基组成及其它操作条件对Ｌ－乳酸发酵的影响。实验结果表明，应用吸附法固定化的米根霉及生物转盘反应器进行Ｌ－乳酸发酵具有发酵速率快，Ｌ－乳酸得率高及既能用于连续发酵又能用于间歇发酵等优点     

米根霉一步发酵法高效积累L-乳酸的策略

考察了2种米根霉发酵生产L-乳酸方法对L-乳酸合成的影响,基于动力学分析,优化了米根霉一步发酵合成L-乳酸的策略.结果表明,与传统发酵相比,一步发酵法能极大降低米根霉产酸过程的延滞期,提高生产强度,但产物比生成速率大大低于传统发酵法.最优的一步法合成L-乳酸的策略为孢子浓度10~5个/mL,葡萄糖浓度100 g/L,蛋白胨3.0 g/L,培养24 h后,菌体密度不变,发酵液体积减少50%.该条件下,发酵阶段发酵时间缩短至13 h,乳酸产量、生产强度和糖酸转化率分别为60 g/L,4.62 g/(L·h)和0.8 g/g,比传统发酵的时间(48 h)和生产强度[1.19 g/(L·h)]分别缩短72.9%和提高288%,比生成速率和糖酸转化率未降低.     

转盘反应器固定米根霉的L—乳酸发酵

研究了米根霉的固定化方法，研制了用吸附法固定米根霉的生物转盘反应器，考察了在该反应器中培养基组织及其它操作条件对Ｌ－乳酸发酵的影响。实验结果表明，应用吸附法固定化的米根霉及生物转盘反应器进行Ｌ－乳酸发酵具有发酵速率快，Ｌ－乳酸得率高及既能用于连续发酵又能用于间歇发酵等优点。     

乳酸生产中的微生物代谢工程

从代谢工程的角度综述了同型及异型乳酸发酵的代谢途径、乳酸菌代谢模型、乳酸脱氢酶在乳酸生产方面的应用、米根霉发酵生产乳酸的代谢工程和基因工程阻断乙醇代谢途径改造乳酸的生产过程等方面的研究进展,讨论了生物信息学及环境胁迫对乳酸代谢的影响,展望了乳酸的微生物代谢工程的发展趋势.     

固定化米根霉在三相流化床中间歇发酵生产L—乳酸的研究

研究了海藻酸钙包埋法固定米根霉在三相流化床反应器中间歇发酵生产Ｌ－乳酸的工艺。实验结果表明，固定化颗粒具有较好的重复使用效果。     

一种新型支架在乳酸发酵中的应用

采用一种新型载体支架来进行米根霉的固定化发酵研究。种子培养过程中,5h后孢子已全部吸附到支架上,种子培养时间为24h,生物量维持在6.8g/L以上;发酵过程中,在温度为33℃,摇床转速为180r/min,装液量为20%,支架数为3个,时间为48h,发酵过程中及时补加CaCO3的条件下,L(+)-乳酸平均浓度可达50.00g/L,转化率接近65.0%,产率可保持在1.0g/(L·h)以上。与游离发酵相比,固定化发酵乳酸浓度、转化率、产率分别提高了79%、250%和150%,发酵周期提前了24h,且能重复发酵7个批次。     

稻草秸秆发酵同时糖化酵解产乳酸的初步研究

本文研究了以稻草秸秆为原料经机械粉碎等处理后,用康宁木霉、黑曲霉、绿色木霉所产纤维素酶和米根霉对其进行同时糖化发酵生产乳酸.本次试验分别采用培养温度、CaCO3的添加次序、装液量、培养时间四个因素,重复试验逐一确定出最优的单因素条件,确定出在最佳试验条件下(培养温度为30℃、每隔24h添加1.5?CO3、装液量为70mL、培养时间为72h).黑曲霉与米根霉同时发酵时产乳酸量可达到22.6mg/ml.     

聚乙烯醇丝固定化米根霉发酵产L（+）-乳酸

以聚乙烯醇(PVA)丝为吸附材料的立体载体,固定化米根霉菌种As3.3462发酵生产乳酸。与游离发酵相比,摇瓶单批固定化发酵乳酸的最终质量浓度提高了25%,发酵时间缩短了33%。分别在摇瓶和鼓泡式反应器中进行了载体的稳定性研究,摇瓶中可稳定发酵10批次,平均转化率为65%,平均产率为1.1g/(L.h);1L鼓泡式生物反应器的放大实验中进行了9批半连续发酵实验,乳酸质量浓度最高达到55.68g/L,转化率69.60%。     

放线菌酮对米根霉积累L-苹果酸代谢途径的调控作用

实验考察了富马酸酶活抑制剂放线菌酮对米根霉发酵产L-苹果酸和富马酸的影响. 结果表明,发酵16 h加入浓度15 mg/L的放线菌酮使米根霉富马酸酶胞质同功酶比活力峰值降低48.7%,而苹果酸脱氢酶胞质同功酶活力却未有明显改变,生成的富马酸比对照样减少37.1%,而L-苹果酸积累量提高54.6%,达到21.7 g/L. 表明通过对米根霉富马酸酶胞质同功酶的抑制作用能减弱米根霉积累富马酸代谢途径中由L-苹果酸向富马酸的转化,从而促进米根霉积累L-苹果酸.     

应用KMnO_4滴定法快速检测米根霉发酵液中富马酸含量

应用KMnO4滴定法快速检测米根霉发酵液中富马酸含量,通过研究富马酸滴定体系下的酸度以及发酵培养基中的葡萄糖和代谢副产物如乳酸、苹果酸、乙醇、草酰乙酸、丁二酸等对KMnO4滴定结果的影响,发现应用KMnO4滴定法测定米根霉发酵液中富马酸的含量,与HPLC检测法测定的含量误差在3%以内,平均回收率为96.86%,相对标准偏差(RSD)为0.27%.以上结论表明,KMnO4滴定法可有效应用于快速检测米根霉发酵液中富马酸的含量.     

EFFECT OF Na+ AND K+ ON MORPHOLOGY AND L-LACTIC ACID PRODUCTIVITY OF Rhizopus oryzae SOI106-3

INTRODUCTION L-lactic acid and its salts are being widely used in the food and Pharmaceutical industries. In particular, lactic acid can be used in the formation of polylactic acid (PLA), a new biodegradable plastic, which will solve one of the world-wide environmental problems, abandoning of waste plastic. Rhizopus oryzae is known to be outstanding in producing optically pure L-lactic acid with low nutritional requirement. Similar to many other mycelial fungal species, Rhizopus cultures are morphology complex. They can grow as extended filamentous form, mycelial mats, mycelial pellets or clumps. Different morphology growth forms can have a significant effect on the rheology of the fermentation broth that will affect O2 transfer and the productivity of strain. In this report, the relationship among the ratio Na+ to K+ in medium, the morphology of the mycelial growth and lactic acid production were studied. We also compared the lactic acid productivity of optimal pellet form with immobilized cells by polyurethane foam.     

Enhanced production of l(+)-lactic acid by floc-form culture of Rhizopus oryzae

A process to optimize l-lactic acid production from glucose by Rhizopus oryzae, based on sustaining floc morphology throughout the fermentation process, is herein performed. During the fermentation, supplementary ammonium sulfate was added intermittently to maintain the ammonia level of the culture medium always higher than 0.1 g/L. With replenish of nitrogen source, mycelia flocs did not aggregate, and the lactic acid production was optimized upon the fermentation being controlled at pH 4.3–4.5 by adding calcium carbonate slurry. In contrast, without supplementary addition of nitrogen source, mycelial clumps formed, resulting in a poor production of lactic acid. In the initial batch fermentation process, the final concentration of lactic acid produced was 109 g/L, with a yield (g lactic acid/g glucose consumed) of 0.87 and a productivity of 2.73 g/L h, using 125 g/L of glucose as substrate. For the first four cycles of repeated-batch fermentation, the average final concentration, the productivity and the yield of lactic acid were 113 g/L, 4.03 g/L h and 0.90, respectively.     

钙离子对米根霉菌体形态及L-乳酸合成的影响

采用添加钙离子的方法,考察钙离子对米根霉菌体形态及L-乳酸发酵合成的影响. 结果表明,添加钙离子有利于球状米根霉形成. 可溶性钙CaCl2浓度越低,越有利于形成较小直径的菌球,利于L-乳酸生成;添加较高浓度的难溶性钙CaCO3 (8.0 g/L除外)能形成较大菌球(约1.5 mm),更有利于L-乳酸合成,产量达58.6 g/L,高于CaCl2的57.2 g/L,平均生产强度为1.22 g/(L×h),高于CaCl2的1.02 g/(L×h). 但过量的CaCO3会包裹菌球,影响L-乳酸合成.     

金属有机骨架材料对大米发酵过程的影响

金属有机骨架材料化工应用是近年来的热点研究课题。但这类材料对生物发酵过程的影响研究报道很少。以大米发酵和Cu-BTC金属骨架材料为例,在发酵过程中加入酒曲（质量分数为0.5%）和Cu-BTC晶体,使用高效液相色谱（HPLC）检测发酵产物中的葡萄糖、乙醇和乳酸的浓度。实验发现,随着Cu-BTC加入量的增加,产物中葡萄糖、乙醇和乳酸的浓度均逐渐降低。此外,MOF-5材料也具有类似的效果。这说明水不稳定的Cu-BTC和MOF-5对于发酵过程有抑制作用。     

Biotechnological production of lactic acid integrated with potato wastewater treatment by Rhizopus arrhizus

This paper describes a feasibility study of a for lactic acid production integrated with are treatment of wastewater from an industrial starch plant. Rhizopus oryzae two strains, Rhizopus arrhizus and Rhizopus oligosporus were tested with respect to their capability to carry out simultaneous saccharification and fermentation to lactic acid using potato wastewater. Rhizopus arrhizus DAR 36017 was identified as a suitable strain that demonstrated a high capacity for starch saccharification and lactic acid synthesis. The optimal conditions, in terms of pH, temperature and starch concentration, for lactic acid production were determined. The selected fungal strain grew well in a pH range from 3.0 to 7.0. The addition of CaCO₃10 g dm^?3 maintained the pH at 5.0–6.0 and significantly enhanced lactic acid production. Kinetic study revealed that almost complete starch saccharification and a lactic acid yield of 450g kg^?1 could be achieved in 20 h and 28 h cultivation, respectively. The maximum lactic acid production 21 g dm^?3 and mycelial biomass (1.7 g dm^?3) were obtained at 30 °C. Besides the multiple bioproducts, total removal of suspended solids and 90% reduction of COD were achieved in a single no‐aseptic operation. Copyright © 2003 Society of Chemical Industry