Gaudreau H, Champagne C P, Conway J, Degré R
Fondation des Gouverneurs, St-Hyacinthe, PQ, Canada.
Can J Microbiol. 1999 Nov;45(11):891-7. doi: 10.1139/w99-089.
Five yeast extracts (YE) were fractionated by ultrafiltration (UF) with 1, 3, and 10 kDa molecular weight cutoff membranes, concentrated by freeze-drying, and the resulting powders of yeast extract filtrates (YEF) were evaluated for their growth-promoting properties on nine cultures of lactic acid bacteria (LAB). There was an increase in alpha-amino nitrogen content of the YEF powders as the pore size of the UF membranes used to filter the YE solutions decreased. The source of YE had a much greater effect than UF on the growth of LAB. This was also the case for the YEF contents in total and alpha-amino nitrogen. Growth curves of the LAB showed that maximum growth rate (mumax) data were on average 30% higher with bakers' YE than with brewers' YE, while maximum optical density (ODmax) values were on average 16% higher with bakers' YE. This could be related to the higher nitrogen content of the bakers' YE used in this study. Modification by UF of the YE had no significant influence on the growth of 4 of the 9 LAB strains. The three strains of Lactobacillus casei were negatively influenced by UF, as they did not grow as well in the media containing the YEF obtained after filtering with 1 and 3 kDa membranes. On a total solids basis, the 2.5 x retentates from the 10 kDa membrane gave, on average, 4% lower mumax and 5% lower ODmax values as compared to cultures where the corresponding YEF was used as medium supplement. This could also be partially related to the different nitrogen contents of the filtrates and retentates.
采用截留分子量为1 kDa、3 kDa和10 kDa的超滤膜对5种酵母提取物（YE）进行分级分离，通过冷冻干燥进行浓缩，然后评估所得酵母提取物滤液（YEF）粉末对9种乳酸菌（LAB）培养物的促生长特性。随着用于过滤YE溶液的超滤膜孔径减小，YEF粉末的α-氨基氮含量增加。YE的来源对LAB生长的影响远大于超滤。总YEF含量和α-氨基氮含量也是如此。LAB的生长曲线表明，使用面包酵母时的最大生长速率（μm ax）数据平均比使用啤酒酵母时高30%，而使用面包酵母时的最大光密度（OD max）值平均高16%。这可能与本研究中使用的面包酵母较高的氮含量有关。超滤对YE的改性对9种LAB菌株中的4种生长没有显著影响。三株干酪乳杆菌受到超滤的负面影响，因为它们在含有用1 kDa和3 kDa膜过滤后获得的YEF的培养基中生长不佳。以总固体为基础，与使用相应YEF作为培养基补充剂的培养物相比，10 kDa膜的2.5倍截留物的μm ax值平均低4%，OD max值平均低5%。这也可能部分与滤液和截留物的不同氮含量有关。
