原料乳及其牧场环境中荧光假单胞菌生物膜环境适应性变化

Study on environmental adaptability of Pseudomonas fluorescein biofilm isolated from raw milk and pasture environment

摘要:

荧光假单胞菌(Pseudomonas fluorescens, P. fluorescens)是原料乳中关键的腐败微生物,在环境中其常在生产设备表面等位点形成生物膜,进而抵抗各种环境压力,导致乳制品腐败变质。本研究首先对我国三个区域中6家牧场的原料乳及其牧场环境样品进行采集,进而对分离出的P. fluorescens进行分型分析并评估其生物膜形成能力,筛选出具有代表性的菌株。通过不同的培养温度,培养条件和培养表面探究P. fluorescens生物膜的环境适应性。结果表明,共分离出25株P. fluorescens,分为5个ST型,其中,P. fluorescens18在24 h和36 h成膜能力更具有稳定性,且OD值均显著高于其他菌株。P. fluorescens18在25_o^C、15_o^C、4_o^C下的TSB(tryptic soy broth, TSB)、脱脂乳、全脂乳培养基中均能产生生物膜,但生成能力不同,培养时间为36 h时,低温抑制P. fluorescens18生物膜胞外物质形成,培养基为乳基时会促进P. fluorescens18生物膜胞外物质形成。扫描电镜结果显示,P. fluorescens18在不锈钢、玻璃和塑料表面上形成生物膜的附着能力不同,分别是不锈钢>玻璃>塑料。

Abstract:

Pseudomonas fluorescens is a key spoilage microorganism in raw milk. In the environment, it often forms biofilms on the surface of production equipment, thus resisting various environmental pressures and leading to spoilage and deterioration of dairy products. In this study, raw milk and farm environment samples from 6 farms in three regions of China were collected, and then the isolated P. fluorescens was classified and its biofilm forming ability was evaluated, and representative strains were screened. The environmental adaptability of P. fluorescens biofilm was investigated by different culture temperatures, culture conditions and culture surface. The results showed that 25 strains of Pseudomonas fluorescens were isolated and divided into 5 ST types. Among them, P. fluorescens 18 had more stable biofilm forming ability at 24 h and 36 h, and OD values were significantly higher than other strains. P. fluorescens 18 can produce biofilm in TSB medium, skim milk medium and whole milk medium at 25 _o^C, 15 _o^C and 4 _o^C, but the production capacity is different. When the culture time is 36 h, low temperature can inhibit the formation of extracellular substances of biofilm of P. fluorescens 18, and the extracellular substances of biofilm of P. fluorescens 18 can be promoted when the medium is milt-based. The results of scanning electron microscopy showed that the adhesion ability of P. fluorescens 18 to form biofilm on the surface of stainless steel, glass and plastic was different, respectively, stainless steel > glass > plastic.