González-Garcinuño Álvaro, Tabernero Antonio, Sánchez-Álvarez José Mª, Galán Miguel A, Martin Del Valle Eva M
Department of Chemical Engineering, University of Salamanca, Plza. Los Caidos s/n, 37007, Salamanca, Spain.
Microb Cell Fact. 2017 May 23;16(1):91. doi: 10.1186/s12934-017-0703-z.
Levan has been traditionally produced from microorganism. However, there is a continuous effort in looking for new strains that improve levan production yield and uses alternative sugar sources for growth. Despite having a wide range of data about levan yield, there are not papers which allow controlling molecular weight, and that plays an essential role for further applications.
The effect of the sucrose concentration on levan yield (and its molecular weight) from Bacillus atrophaeus and Acinetobacter nectaris (Gram positive and Gram negative respectively) was studied in this work. It was found that A. nectaris growth (from 3 to 1.5 g L in 40 h) and its levan production (from 3 to 1.5 g L) decreases by increasing sucrose concentration (best results at a concentration of 120 g L) whereas B. atrophaeus growth (3.5 g L in 30 h) and its levan production (also 3.5 g L) were not affected by modifying that parameter. Levan molecular weight from A. nectaris decreases by increasing sucrose concentration (from 8000 to 2000 kDa) whereas levan molecular weight from B. Atrophaeus remains always around 50 kDa. By performing a kinetic study, it was shown that A. nectaris growth follows a substrate-inhibition model, whereas Monod equation provided a good fit for B. atrophaeus growth. Finally, wastes from orange juice industry were used as a medium culture to cultivate those microorganism, obtaining good results with B. atrophaeus (growth 3 g L in 30 h).
Levan production kinetics was determined and compared between different bacteria types.
传统上，果聚糖是由微生物生产的。然而，人们一直在不断努力寻找能够提高果聚糖产量并利用替代糖源进行生长的新菌株。尽管有大量关于果聚糖产量的数据，但尚无能够控制分子量的相关论文，而分子量对于进一步应用起着至关重要的作用。
本研究考察了蔗糖浓度对萎缩芽孢杆菌和花蜜不动杆菌（分别为革兰氏阳性菌和革兰氏阴性菌）果聚糖产量（及其分子量）的影响。研究发现，随着蔗糖浓度的增加，花蜜不动杆菌的生长（40小时内从3克/升降至1.5克/升）及其果聚糖产量（也从3克/升降至1.5克/升）下降（在120克/升的浓度下效果最佳），而萎缩芽孢杆菌的生长（30小时内达到3.5克/升）及其果聚糖产量（同样为3.5克/升）不受该参数变化的影响。随着蔗糖浓度的增加，花蜜不动杆菌产生的果聚糖分子量下降（从8000 kDa降至2000 kDa），而萎缩芽孢杆菌产生的果聚糖分子量始终保持在50 kDa左右。通过动力学研究表明，花蜜不动杆菌的生长遵循底物抑制模型，而莫诺德方程能很好地拟合萎缩芽孢杆菌的生长。最后，将橙汁工业废料用作培养基来培养这些微生物，萎缩芽孢杆菌取得了良好的结果（30小时内生长至3克/升）。
确定并比较了不同类型细菌的果聚糖生产动力学。
