Fluorescent In Situ Hybridization Analysis of Open Lactic Acid Fermentation of Kitchen Refuse Using rRNA-Targeted Oligonucleotide Probes

摘要

Reproducible amounts of lactic acid accumulate in minced kitchen refuse under open conditions with intermittent pH neutralization [Sakai et al.,Food Sci.Technol.Res.,6,140(2000)].Here,we showed that such pH-controlled open fermentation of kitchen refuse reproducibly resulted a selective proliferation of a major lactic acid bacterial(LAB)species.In one experiment,the predominant microorganisms isolated during the early phase(6 h)were Gammaproteobac-teria.In contrast,those that predominated during the late phase(48 h)were always Lactobacillus plant arum in three independent experiments.To further quantify the microbial community within open lactic acid fermentation,we performed fluorescent in situ hybridization(FISH)analysis targeting 16S(23S)rRNA.We designed two new group-specific DNA probes:LAC722(L)was active for most LAB including the genera Lactobacillus,Pediococcus,Leuconostoc and Weisella,whereas Lplan477 was specific for L.plantarum and its related species.We then optimized sample preparation using lysozyme and hybridization conditions including temperature,as well as the forma-mide concentration and the salt concentration in the washing buffer.We succeeded in quantification of microorganisms in semi-solid,complex biological materials such as minced kitchen refuse by taking color microphotographs in modified RGB balance on pre-coated slides.FISH analysis of the fermentation of kitchen refuse indicated that control of the pH swing leads to domination by the LAB population in minced kitchen refuse under open conditions.We also confirmed that L.plantarum,which generates lactic acid in high quantities but with low optical activity,became the dominant microorganism in kitchen refuse during the late phase of open fermentation.