Kumar Nirmal, Kumar Vinay, Waheed Syed Mohsin, Pradhan Diwas
Department of Biotechnology, Graphic Era (Deemed to be University), 566/6 Bell Road, Society Area, Clement Town, 248002 Dehradun, Uttarakhand, India.
Dairy Microbiology Division, ICAR-National Dairy Research Institute, GT Rd, 132001 Karnal, Haryana, India.
Food Technol Biotechnol. 2020 Dec;58(4):359-369. doi: 10.17113/ftb.58.04.20.6728.
In the current scenario of milk production in developing and developed countries, several factors influence the shelf-life of raw milk and add significant numbers of microbial contaminants that drastically lower the initial microbial quality leading to milk spoilage by the time it reaches the processing units.
The present study was undertaken to investigate the biopreservative efficacy of reuterin system along with different combinations of bacteriocins in controlling the initial microflora of raw milk at farm level. strain LR47, having effective antimicrobial activity, was shortlisted from our previous study and further characterized for reuterin production and tested in raw milk system.
Preliminary testing of the cell-free supernatant from LR47 demonstrated significant growth inhibition of the majority of the tested bacterial indicators of milk spoilage. Further genetic analysis of the LR47 revealed the presence of two genes ( and ) involved in the utilization of glycerol to produce reuterin two different pathways. The strain LR47 was also found to possess comparatively higher capacity to convert glycerol into reuterin when checked through colorimetric assay. In the raw milk biopreservation experiment with reuterin alone or in combination with bacteriocins, the highest level of growth suppression in the total bacterial load and coliform counts was observed in the sample that was treated with a combination of reuterin, nisin and pediocin. The treatment combining these three natural biopreservatives at specific concentrations was able to maintain the initial microbial quality and extend the shelf-life of raw milk by 6 h at 37 °C based on the microbial counts and physicochemical properties, . pH and titratable acidity. In conclusion, the results confirm that the use of reuterin in combination with bacteriocins is a promising approach for temporary control of the raw milk microflora and extension of its shelf-life until further processing.
This study demonstrates for the first time the use of reuterin for the extension of shelf-life of raw milk as an alternative treatment method.
在发展中国家和发达国家当前的牛奶生产情况下，有几个因素会影响生牛奶的保质期，并增加大量微生物污染物，这些污染物会大幅降低初始微生物质量，导致牛奶在到达加工单位时就已变质。
本研究旨在调查罗伊氏乳杆菌素系统与不同组合的细菌素在农场层面控制生牛奶初始微生物群落方面的生物保鲜效果。从我们之前的研究中筛选出具有有效抗菌活性的LR47菌株，并进一步对其罗伊氏乳杆菌素的产生进行表征，并在生牛奶系统中进行测试。
对LR47菌株的无细胞上清液进行的初步测试表明，对大多数测试的牛奶腐败细菌指标有显著的生长抑制作用。对LR47菌株的进一步基因分析揭示了存在两个参与利用甘油通过两条不同途径产生罗伊氏乳杆菌素的基因（ 和 ）。通过比色法检测发现，LR47菌株将甘油转化为罗伊氏乳杆菌素的能力也相对较高。在单独使用罗伊氏乳杆菌素或与细菌素联合使用的生牛奶生物保鲜实验中，在使用罗伊氏乳杆菌素、乳酸链球菌素和片球菌素组合处理的样品中，观察到总细菌负荷和大肠菌群计数的生长抑制水平最高。基于微生物计数和理化性质（pH值和可滴定酸度），将这三种天然生物防腐剂以特定浓度组合使用，能够在37°C下维持生牛奶的初始微生物质量，并将其保质期延长6小时。总之，结果证实，将罗伊氏乳杆菌素与细菌素联合使用是一种有前景的方法，可暂时控制生牛奶的微生物群落，并延长其保质期直至进一步加工。
本研究首次证明了使用罗伊氏乳杆菌素作为一种替代处理方法来延长生牛奶的保质期。
