ABSTRACT Cr (VI) being used in various activities of industries and its improper treatment lead to contamination of environment. Among different methods, biological is the most efficient method to control pollution from soils affected with metals. Present study was designed to assess the role of Paenibacillus thiaminolyticus PS5 for adsorption, Cr (VI) reduction and mechanism of reduction. Sorption of chromium (VI) by strain PS5 was obtained by batch equilibrium method. Cr (VI) reduction in both free and immobilised cells were evaluated by 1,5-Diphenyl Carbazide method. The formation of biofilm by Paenibacillus thiaminolyticus PS5 was observed for colour change as well as quantified spectrophotometrically. Analysis kits were used to measure the amount of eDNA, superoxide and malondialdehyde (MDA). Metal resistant strain PS5 was characterised as P. thiaminolyticus using 16S rRNA gene sequence. Maximum biosorption of Cr (VI) by strain PS5 was found at pH 6–8 and 100–400 µgCr/mL within 24 hours of incubation. Complete reduction of Cr (VI) by strain PS5 was achieved at pH 6–8 and100–300 µg/mL Cr (VI). Paenibacillus thiaminolyticus PS5 immmobilisation on sodium alginate and polyvinyl alcohol facilitated complete reduction of Cr (VI) within 18 hours due to the formation of more biofilm under metal stress conditions. Strain PS5 reduced almost all Cr (VI) into Cr (III) in supernatant, most of which was immobilised by cell debris. Experiments confirmed the reduction of Cr (VI) by cytosolic cell-free extracts which is a mechanism of detoxification. The release of exopolysaccharides and antioxidants by strain PS5 played a protective role against cell damage by Cr (VI) as Cr (VI) could not release the significant amount of eDNA, superoxide and MDA. The present study proved strain PS5 to be a super bioinoculant which has great capacity for adsorption, biotransformation and can activate cytosolic reductases, exopolysaccharides and antioxidants against oxidative damage.

中文翻译：

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Paenibacillus thiaminolyticus PS 5 的 NADH 依赖性铬还原酶、胞外多糖和抗氧化剂对活性氧诱导的损伤的作用

摘要 Cr (VI) 用于工业的各种活动及其不当处理导致环境污染。在不同的方法中，生物是控制受金属影响的土壤污染的最有效方法。本研究旨在评估类芽孢杆菌 PS5 在吸附、Cr (VI) 还原和还原机制方面的作用。通过分批平衡法获得菌株 PS5 对铬 (VI) 的吸附。游离和固定细胞中 Cr (VI) 的减少通过 1,5-二苯基碳酰肼方法进行评估。观察到由 Paenibacillus thiaminolyticus PS5 形成的生物膜的颜色变化以及分光光度法定量。分析试剂盒用于测量 eDNA、超氧化物和丙二醛 (MDA) 的含量。金属抗性菌株 PS5 被表征为 P。thiaminolyticus 使用 16S rRNA 基因序列。在培养 24 小时内，在 pH 6–8 和 100–400 µgCr/mL 条件下，发现菌株 PS5 对 Cr (VI) 的最大生物吸附。在 pH 6–8 和 100–300 µg/mL Cr (VI) 条件下，PS5 菌株完全还原了 Cr (VI)。由于在金属胁迫条件下形成更多的生物膜，将类芽孢杆菌 PS5 固定在海藻酸钠和聚乙烯醇上有助于在 18 小时内完全还原 Cr (VI)。菌株 PS5 将上清液中的几乎所有 Cr (VI) 还原为 Cr (III)，其中大部分被细胞碎片固定。实验证实，细胞溶质无细胞提取物可减少 Cr (VI)，这是一种解毒机制。PS5 菌株释放的胞外多糖和抗氧化剂对 Cr (VI) 造成的细胞损伤起到了保护作用，因为 Cr (VI) 不能释放大量的 eDNA、超氧化物和 MDA。本研究证明菌株 PS5 是一种超级生物接种剂，具有很强的吸附、生物转化能力，可以激活细胞溶质还原酶、胞外多糖和抗氧化剂以抵抗氧化损伤。