稀土离子对米根霉菌产L-乳酸的影响

目的 :研究稀土离子对米根霉菌的生长,L-乳酸产量和产率的影响。方法 :通过在米根霉菌培养的初期和对数期加入浓度为10~(-4)mol/L,10~(-5)mol/L和10~(-6)mol/L的Dy~(3+)和Er~(3+)来研究稀土离子对米根霉菌的生长,L-乳酸产量和产率的影响。结果:在对数期加入不同浓度的稀土离子对菌体的生长不产生影响,在培养初期加入10-5mol/L Dy3+和10-6mol/L Er3+促进菌体在稳定期的生长,并对菌种L-乳酸的产量和产率影响差异极显著。在培养初期加入10~(-5)mol/L Dy~(3+)时,L-乳酸产量较对照组提高9.5%,产率达到了96.4%。在培养的初期加入10~(-6)mol/L的Er~(3+)时,L-乳酸产量较对照组提高12.8%,产率为99.3%。结论 :稀土对米根霉菌的生长和L-乳酸的产量都会产生影响,本研究可为L-乳酸的发酵提供重要参考。     

L-乳酸的微生物发酵

L-乳酸作为一种环境友好新兴材料,广泛应用于制药、食品、皮革等工业中,由于可降解塑料生产量的增加,对于其需求也越来越多。乳酸生产的主要方法是微生物发酵法,包括细菌发酵法和根霉发酵法,本文对于这两种微生物发酵方法进行了综述。     

高产L-乳酸米根霉的选育

经过紫外诱变获得一株来根霉菌株R8416产L-乳酸高，产酸稳定．探讨了不同氮源、通气量、培养基配方、中和剂等发酵条件对其产L-乳酸的影响。试验结果表明．该菌株最适发酵培养基组成(％)：淀粉水解糖11，MgSO4、0.025．KH2PO4 0．06．ZnSO4 0．004．CaCO3 6．pH自然。8批平均产L-乳酸85．9g／L，对糖转化率80．3％，发酵周期50h，几乎不舍杂酸．L-乳酸旋光纯度与Purac公司乳酸相当。     

L-乳酸气升式发酵罐条件的优化

对通过诱变选育获得一株米根霉菌株R8416在气升式发酵罐中的行为条件进行了研究，探讨了淀粉液化、接种量、DO（溶解氧）、pH、中和剂等发酵条件对其产L-乳酸的影响。试验结果表明，在适当的发酵条件下该菌种对糖的转化率达到了80％。产酸率在9．8％以上，发酵周期小于48小时。     

发酵生产L-乳酸的现状与展望

L-乳酸是一种有多种用途的重要的有机酸。概述了生产制备L-乳酸的方法及其优缺点,着重综述了微生物发酵法生产L-乳酸的研究现状,并展望了其发展前景。     

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。     

用于固定化米根霉发酵生产L-乳酸的转盘反应器及其放大

利用米根霉菌丝体发达且易于吸附在固体表面的特性,将其固定化于转盘表面,利用转盘反应器实现L 乳酸的固定化发酵。考察了固定化过程中的底物浓度、产物浓度和溶解氧浓度的变化规律。在此基础上,进一步研究了8L反应器的通气量、装液量及转盘转速等操作参数对发酵过程的影响,得到了优化的反应器操作条件。最后,利用自制的1m3反应器考察了转盘反应器固定化发酵的可行性,得到了比较满意的结果,证实该反应器具有良好的工业应用前景。     

米根霉发酵生产L(+)-乳酸研究进展

米根霉是生产绿色平台生物化学品L(+) 乳酸的理想菌种 ,目前集中在发酵工艺的优化、新型生物反应器的设计以及细胞固定化等方面的研究 ,通过控制米根霉菌体形态使之自聚集成为一定大小的球体进行乳酸发酵 ,操作简便、费用低。建议今后从应用代谢工程技术定向选育米根霉L(+) 乳酸高产菌 ,改进发酵设备、改良提取工艺 ,合理控制乳酸产品的构型等几个方面着手进行进一步研究 ,从而降低乳酸生产原料的成本 ,扩大L(+) 乳酸的应用领域。     

Repeated-Batch and Continuous Production of L-Lactic Acid by Rhizopus oryzae Immobilized in Calcium Alginat Beads: Reactor Performance and Kinetic Model

Repeated-batch and continuous production of L-lactic acid by immobilized Rhizopusoryzae with calcium alginate entrapment method in a three-phase fluidized-bed bioreactor was stud-ied.The operation conditions were optimized.The productivity based on total reactor volume wasabout 3 times higher than that with free cells in a traditional stirred tank bioreactor.A mathemat-ical model was proposed and the model predictions were in good agreement with the experimentaldat.     

米根霉在5L发酵罐种子培养过程中的形态控制

发酵过程中控制菌体为适宜的菌球形态对于丝状真菌发酵的工业化放大具有重要的研究意义.本文针对米根霉在5 L发酵罐上种子培养过程中的形态学控制进行了研究,确定了最适宜形成菌球的培养条件分别为:控制发酵罐内的孢子浓度在5×104～8.3×104/mL的范围内,搅拌转速350 r/min,种子液pH值稳定在2.80,以20g/L的葡萄糖浓度作为最佳种龄的经验值确定种子培养时间为52 h.该条件下可以获得表面光滑的直径约为1 mm的结实茵体.发酵结果表明,相比于絮状形态,菌球形态更有利于富马酸的生成.     

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     

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.     

Extractive fermentation for fumaric acid production by Rhizopus oryzae

Low product concentration and high cost of recovery process have motivated the study of in situ removal of fumaric acid from fermentation broth. After a series of screenings, an integrated process with fumaric acid fermentation and extraction was developed. Under this integrated process, fumaric acid production and productivity increased from 18.06 g/L to 34.23 g/L, and from 0.27 g/L/h to 0.57 g/L/h, respectively. Neutralizing agent utilization decreased by 58.75%, and 140.7 g/L ammonium fumarate was obtained after back extraction, which could be directed used to produce related derivatives without concentration. Thus, the integrated process was more economic and environmental friendly.     

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.     

Lipolytic Enzyme Production by Immobilized Rhizopus oryzae

In this paper, a suitable technique as well as an adequate material for the immobilization of the fungus Rhizopus oryzae were investigated. This organism has been shown to have potential in the field of food aroma due to the production of extracellular lipolytic enzymes. However, an efficient production system at bioreactor scale for its application to the flavor compounds production is still needed. Among the supports studied, alginate beads were the best carrier materials, leading to the highest lipolytic activities of up to 400 U/L after 3 days of cultivation. Repeated batch cultures were carried out to improve cell concentration and lipolytic activity. The gel beads produced lipolytic enzyme under optimized conditions for consecutive batch fermentations without marked activity loss and deformation attained a maximum level of 715 U/L after three batches. The production of lipolytic enzyme by immobilized Rhizopus oryzae in a 2‐litre airlift bioreactor with the optimized conditions was evaluated. Lipolytic activities of 487 U/L were attained, operating in successive batches without operational problems and the bioparticles (the fungus grows in alginate beads) maintained their shape throughout fermentation.