米根霉菌球特性对乳酸发酵的影响

Effects of pellet characteristics on L-lactic acid fermentation by Rhizopus oryzae

摘要:

摘要:【目的】考察了接种量、蛋白胨和CaCO3浓度对菌球特性(形态、大小、密度和内部结构)的影响，并结合菌球内部结构深入剖析了菌球特性对乳酸发酵的影响。【方法】将孢子液接入到含不同蛋白胨和CaCO3浓度的种子培养基，控制不同的初始孢子浓度，培养36 h，用图像分析软件进行菌球内部聚集形态结构分析，并进行乳酸发酵。【结果】结果表明，接种量是影响菌球形成以及大小的重要因素，接种量越大，菌球直径越小;蛋白胨浓度对菌球密度影响最大，浓度越高密度越大;CaCO3浓度主要影响孢子萌发以及菌丝分枝频率。【结论】菌球密度是影响乳酸产量最显著的因素，低密度的菌球易形成较薄外层和内部菌丝松散或者中空的结构，乳酸产量低，乳酸产量随着密度而增加，当密度增大到50－60 kg/m3时，菌球内部形成外层较厚且紧密程度分布均一和内部较为松散的结构，此时乳酸产量最大;当密度过大时，菌球内部结构致密，影响传氧传质，导致产量下降。

Abstract:

Abstract:［Objective］ Effects of pellet morphology，diameter，density，and interior structure on L-lactic acid fermentation by Rhizopus oryzae were characterized for different inoculum sizes and concentrations of peptone and CaCO3.［Methods］ Different initial spore concentrations were inoculated in the preculture medium with different peptone and CaCO3 concentrations，and cultivated at 30℃ for 36 h. Representative pellets were chosen for interior structure analysis and L-lactic acid production.［Results］ Inoculum size was the most important factor determining pellet formation and diameter． Peptone concentration had the greatest effect on pellet density. L-lactic acid production depended heavily on pellet density but not on pellet diameter． Low-density pellets formed easily under conditions of low peptone concentration and often had a relatively hollow structure．This structure greatly decreased production．The production of L-lactic acid increased until the density reached a certain level (50－60 kg/m3)，which the compact part distributed homogeneously in the thick outer layer of the pellet，and loose in the central layer．Homogeneously structured，denser pellets limited mass transfer．CaCO3 concentration only had a slight influence on pellet diameter and density.［Conclusion］ This work provides the insight into pellet structure and its relationship with productivity.