Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea.
Department of Food and Biotechnology, College of Science and Technology, Korea University, Sejong 30019, Republic of Korea.
Food Res Int. 2022 Jun;156:111332. doi: 10.1016/j.foodres.2022.111332. Epub 2022 May 5.
The microbiological safety of reconstituted infant formula (RIF) has focused on infectious pathogens, whereas the risk of spore-forming bacteria (SFB) has been limited to spoilage and toxin production. This study suggests an underrecognized niche of SFB as nitrite producers during the handling of RIF. The production of nitrite along with the bacterial growth of 133 nitrite-producing SFB isolated from infant formula processing environments and end-products (70 mesophiles and 63 thermophiles) under RIF handling conditions were analysed. Most mesophiles (68 out of 70) and two thermophiles showed nitrite production during growth at 30 °C or 40 °C. Vigorous producers of nitrite [Bacillus sp. strains (FHS-PPBM449, 481, 236, 237)] showed a rapid onset of nitrite production (within 4 h). In particular, FHS-PPBM449 (2-3 log CFU/mL) exhibited the shortest onset time (210 min) and a nitrite production level up to 521 µM in RIF with 100 ppm nitrate at 40 °C. Overall, the results of the maximum level of nitrite produced by vigorous nitrite producers indicate that infants can consume more than seven times the acceptable daily intake of nitrite (0.74 mg for 12-month-old infants with an average body weight), even via a single feeding of RIF. An analysis of the relationship of the onset time of nitrite production with the bacterial concentration based on predictive models suggests that the growth of SFB up to 5-6 log CFU/mL is regarded as a prerequisite for nitrite production. This study revealed an underreported source of nitrite from RIF handling conditions, and the rapid onset of a high level of nitrite production from SFB should be the major target in the establishment of intervention strategies against nitrite as a microbial risk.
再配制婴儿配方食品（RIF）的微生物安全性一直集中在传染性病原体上，而形成孢子的细菌（SFB）的风险仅限于变质和毒素产生。本研究表明，在处理 RIF 时，SFB 作为亚硝酸盐生产者是一个被低估的生态位。分析了从婴儿配方食品加工环境和终端产品（70 个中温菌和 63 个高温菌）中分离出的 133 株 SFB 在 RIF 处理条件下的亚硝酸盐产生和细菌生长情况。大多数中温菌（70 株中的 68 株）和 2 株高温菌在 30°C 或 40°C 生长时产生亚硝酸盐。亚硝酸盐的强产生菌[芽孢杆菌属菌株（FHS-PPBM449、481、236、237）]表现出亚硝酸盐产生的快速起始（在 4 小时内）。特别是 FHS-PPBM449（2-3 对数 CFU/mL）在 40°C 下，RIF 中硝酸盐浓度为 100ppm 时，表现出最短的起始时间（210 分钟）和高达 521µM 的亚硝酸盐产生水平。总的来说，强亚硝酸盐产生菌产生的亚硝酸盐最大水平的结果表明，即使通过单次喂养 RIF，婴儿也可以摄入超过可接受的每日亚硝酸盐摄入量（12 个月大的婴儿平均体重为 0.74mg）的七倍。基于预测模型对亚硝酸盐产生起始时间与细菌浓度的关系进行分析表明，SFB 的生长达到 5-6 对数 CFU/mL 被认为是亚硝酸盐产生的前提条件。本研究揭示了 RIF 处理条件下亚硝酸盐的一个未被充分报道的来源，从 SFB 中快速产生高水平的亚硝酸盐应该是制定针对亚硝酸盐作为微生物风险的干预策略的主要目标。
