Booysena C, Dicks L M T, Meijering I, Ackermann A
Department of Microbiology, University of Stellenbosch, South Africa.
Int J Food Microbiol. 2002 Jun 5;76(1-2):63-73. doi: 10.1016/s0168-1605(02)00007-7.
Malt has a complex microbial population, which changes as the malting process commences. Little is known about the proliferation of lactic acid bacteria (LAB) in each of the malting phases. In this study, we determined the number of LAB present in the different phases of malting with Clipper and Prisma barley cultivars. The strains were identified to species level by using numerical analysis of total soluble cell protein patterns, RAPD-PCR banding patterns and 16S rRNA sequencing. The number of viable LAB in the barley before steep was higher in Prisma than Clipper (7.6 x 10(4) and 1.2 x 10(3) cfu/g, respectively). Despite this, the number of viable cells recorded in the first steep water was slightly higher for Clipper (9.0 x 10(5) cfu/g) than Prisma (5.5 x 10(5) cfu/g). More or less, the same cell numbers were recorded for the two barley cultivars after the first and second dry stands. Both cultivars displayed more or less the same cell numbers (3.7 x 10(7) for Clipper and 3.2 x 10(7) cfu/g for Prisma) after the third day of germination. However, a higher number of LAB were detected in the kilned Prisma malt (6.9 x 10(4) cfu/g) than the Clipper malt (1.5 x 10(4) cfu/g). Leuconostoc argentinum, Le. lactis and Weissella confusa were the most predominant in both cultivars. A few strains were identified as W. paramesenteroides (four strains), Lactobacillus casei (five strains), Lactococcus lactis (five strains) and Lb. rhamnosus (two strains). Lb. casei and Lb. rhamnosus were not isolated from the Prisma cultivar, while W. paramesenteroides and Lc. lactis were absent in the Clipper cultivar. Kilned malt of the Clipper cultivar contained predominantly Le. argentinum, whereas the Prisma cultivar contained mainly Lc. lactis. To our knowledge. this is the first report of LAB in Clipper and Prisma barley and the various malting phases. The influence of the various groups of lactic acid bacteria on the fermenting ability of brewers' yeast is currently being determined.
麦芽具有复杂的微生物群落，随着制麦过程的开始而发生变化。关于乳酸菌（LAB）在每个制麦阶段的增殖情况，人们了解甚少。在本研究中，我们测定了Clipper和Prisma大麦品种在制麦不同阶段的乳酸菌数量。通过对总可溶性细胞蛋白图谱、RAPD-PCR条带图谱和16S rRNA测序进行数值分析，将菌株鉴定到种水平。浸麦前大麦中乳酸菌的活菌数，Prisma品种高于Clipper品种（分别为7.6×10⁴和1.2×10³ cfu/g）。尽管如此，Clipper品种在第一次浸麦水中记录的活菌数（9.0×10⁵ cfu/g）略高于Prisma品种（5.5×10⁵ cfu/g）。在第一次和第二次干燥静置后，两个大麦品种记录的细胞数大致相同。在发芽第三天后，两个品种的细胞数大致相同（Clipper品种为3.7×10⁷，Prisma品种为3.2×10⁷ cfu/g）。然而，在烘焙后的Prisma麦芽中检测到的乳酸菌数量（6.9×10⁴ cfu/g）高于Clipper麦芽（1.5×10⁴ cfu/g）。阿根廷明串珠菌、乳酸明串珠菌和类肠膜魏斯氏菌在两个品种中最为常见。少数菌株被鉴定为副肠膜魏斯氏菌（4株）、干酪乳杆菌（5株）、乳酸乳球菌（5株）和鼠李糖乳杆菌（2株）。干酪乳杆菌和鼠李糖乳杆菌未从Prisma品种中分离出来，而副肠膜魏斯氏菌和乳酸乳球菌在Clipper品种中不存在。Clipper品种的烘焙麦芽主要含有阿根廷明串珠菌，而Prisma品种主要含有乳酸乳球菌。据我们所知，这是关于Clipper和Prisma大麦以及各个制麦阶段乳酸菌的首次报告。目前正在确定不同组乳酸菌对啤酒酵母发酵能力的影响。
