Zhao Ning, Zhang Yi, Li Jun, Xu Junnan, Jiao Lingxia, Hu Kaidi, Li Qin, Li Jianlong, Liu Aiping, Fan Mingtao, Liu Shuliang
College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, China.
College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China.
Int J Food Microbiol. 2025 Feb 16;430:111058. doi: 10.1016/j.ijfoodmicro.2025.111058. Epub 2025 Jan 6.
Acid adaptive response (AAR) is a survival mechanism that allows bacteria to develop enhanced stress tolerance. Our previous research identified AAR in Alicyclobacillus acidoterrestris, a thermo-acidophilic bacterium responsible for fruit juice spoilage. However, the roles of specific acidulants, adaptive temperatures, and acidic juice matrices in triggering AAR remain elusive. In this work, acid adaptation of A. acidoterrestris in broth acidified with various organic acids and in fruit juices was investigated, while also considering the ambient temperature. Results revealed that acid adaptation (at pH values of 3.0, 3.2, and 3.5, adjusted with malic, tartaric, or citric acids, and at pH 3.5 adjusted with lactic, succinic, or ascorbic acids, for 1 h) enhanced acid resistance (pH = 2.2, 1 h) of A. acidoterrestris, across all tested temperatures (45 °C, 35 °C, 25 °C, and 10 °C). Moreover, heat tolerance (65 °C, 5 min) was improved, except when using tartaric acid. Among acidulants used during adaptation (pH 3.5, 45 °C), succinic acid induced the highest level of acid resistance, followed by lactic, citric, malic, ascorbic, and tartaric acids, in descending order. For heat resistance, the ranking was succinic, citric, tartaric, lactic, ascorbic, and malic acids. Furthermore, acid adaptation in apple or orange juices enhanced heat resistance (65 °C) of A. acidoterrestris, and the induced resistance increased with extension of adaptation period. Adaptive temperatures of 25 °C and 35 °C were more effective in promoting resistance than 10 °C. These findings highlight the importance of considering adaptive responses of A. acidoterrestris to different preservation stresses and acidic juice environments during juice processing.
酸适应性反应（AAR）是一种生存机制，使细菌能够增强对压力的耐受性。我们之前的研究在嗜酸耐热芽孢杆菌中发现了AAR，该菌是一种导致果汁腐败的嗜热嗜酸细菌。然而，特定酸化剂、适应温度和酸性果汁基质在触发AAR中的作用仍然不清楚。在这项工作中，研究了嗜酸耐热芽孢杆菌在各种有机酸酸化的肉汤和果汁中的酸适应性，同时考虑了环境温度。结果表明，酸适应（在pH值为3.0、3.2和3.5时，用苹果酸、酒石酸或柠檬酸调节，在pH 3.5时用乳酸、琥珀酸或抗坏血酸调节，持续1小时）增强了嗜酸耐热芽孢杆菌在所有测试温度（45℃、35℃、25℃和10℃）下的耐酸性（pH = 2.2，1小时）。此外，耐热性（65℃，5分钟）得到了提高，但使用酒石酸时除外。在适应过程中使用的酸化剂（pH 3.5，45℃）中，琥珀酸诱导的耐酸性水平最高，其次是乳酸、柠檬酸、苹果酸、抗坏血酸和酒石酸，顺序依次降低。对于耐热性，顺序为琥珀酸、柠檬酸、酒石酸、乳酸、抗坏血酸和苹果酸。此外，在苹果汁或橙汁中的酸适应增强了嗜酸耐热芽孢杆菌的耐热性（65℃），并且诱导的抗性随着适应期的延长而增加。25℃和35℃的适应温度比10℃更有效地促进抗性。这些发现突出了在果汁加工过程中考虑嗜酸耐热芽孢杆菌对不同保存压力和酸性果汁环境的适应性反应的重要性。
