Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, South Korea.
Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, South Korea.
Food Microbiol. 2019 Jun;80:50-61. doi: 10.1016/j.fm.2018.12.012. Epub 2018 Dec 24.
Although nitrite in powdered milk formula (PIF) is a recognized health risk for infants, the presence of nitrite in PIF has only been investigated as a chemical contaminant during the inspection of end-products. The risk posed by microbial sources of nitrite during the PIF manufacturing process has not been considered. This is the first study to report the taxonomy and physiological characteristics of nitrite-producing bacteria isolated from PIF processing environments. All isolates identified as nitrite-producers (133 out of 501 strains collected over four years) from work-in-process and end-products of PIF were spore-forming bacilli. Nitrite-producing metabolism under PIF processing conditions was found in not only thermophilic isolates (3 Bacillus, 60 Geobacillus from 63 strains; 100%) but also in mesophilic isolates (65 Bacillus, 1 Anoxybacillus from 70 strains; 65.7%). Geobacillus was the only highly heat-resistant sporeformer and vigorous nitrite-producer exhibiting dramatic increases in nitrite over short periods of incubation (a maximum value within 3 h). High conversions of nitrate to nitrite (up to 88.8%) was also observed, highlighting bacteria as a key source of nitrite in PIF processing lines. Further research into the diversity of metabolic activity observed in this study can facilitate specialized management of nitrite-producers in PIF processing lines.
尽管奶粉配方中的亚硝酸盐（Nitrite）被认为是婴儿的健康风险因素，但在对最终产品的检查中，才将亚硝酸盐在奶粉配方中的存在作为化学污染物进行调查。在奶粉配方生产过程中，微生物来源的亚硝酸盐所带来的风险尚未被考虑。本研究首次报道了从奶粉加工环境中分离出的亚硝酸盐产生菌的分类和生理特性。从奶粉生产过程中的工作流程和最终产品中分离出的所有亚硝酸盐产生菌（在四年内收集的 501 株菌中分离出 133 株）均为产芽孢的杆菌。在奶粉加工条件下，不仅在嗜热菌（3 株芽孢杆菌，63 株中 6 株耐热芽孢杆菌；100%）中发现了亚硝酸盐产生代谢，在中温菌（65 株芽孢杆菌，70 株中 1 株嗜冷芽孢杆菌；65.7%）中也发现了亚硝酸盐产生代谢。仅有耐热芽孢杆菌是高度耐热的产芽孢菌和强亚硝酸盐产生菌，在短时间的孵育过程中（在 3 小时内达到最大值），亚硝酸盐的急剧增加。还观察到硝酸盐向亚硝酸盐的高转化率（高达 88.8%），这突出了细菌是奶粉加工线中亚硝酸盐的关键来源。进一步研究本研究中观察到的代谢活性多样性，可以促进在奶粉加工线中对亚硝酸盐产生菌进行专门管理。
