Abstract

Bioremediation using microorganisms have become innovative efficient tools for detoxifying a wide variety of urban and industrial wastewaters. In this study, we investigated for the first time the microbial detoxification of phosphate processing wastewaters (PPWW) by using the indigenous bacterium Serratia rubidaea NCTC12971, having numerous plant growth promoting traits. In fact, the isolated strain exhibited an attractive capacity of phosphate solubilization, siderophore production as well as indole acetic acid (IAA) secretion. Additionally, the strain has significant antifungal effect against Alternaria alternata. The monitoring of the bacterial growth at increasing concentrations of heavy metals showed minimum inhibitory concentrations (MICs) of 8, 6, 3 and 3 mg L⁻¹, respectively for Pb, Cd, Cu and Zn. The 10-days treatment of PPWW by Serratia rubidaea significantly decreases its salinity in terms of electrical conductivity (EC), its chemical oxygen demand (COD), its biochemical oxygen demand (BOD₅) and its total organic carbon (TOC). Regarding heavy metals removal, the detoxification rates were 94.4, 91.5, 85, and 66.5%, for Pb, Cd, Cu, and Zn, respectively. Moreover, the biological treatment of the PPWW declines its phytotoxicity toward lentils (Lens culinaris) and chickpea (Cicer arietinum) seeds germination. Hence, with the PPWW, the germination indices (GI) of chickpea (Cicer arietinum) and lentils (Lens culinaris) were 16.6 and 10%, respectively. While, with the biological treated (BTPPWW), the GI were significantly increased to approximately 76.6% for both seeds mentioned. Such results strengthened the potential use of Serratia rubidaea NCTC12971 for the establishment of biotechnological process aiming to minimize the harmful effects of PPWW as well as its use as plant growth promoting bacteria (PGPB).

• Highlights

• This study is the first report investigating the potential use of indigenous bacteria in the bio-treatment of wastewaters discharged from the Tunisian phosphate laundries units.

• Serratia rubidaea NCTC12971 was selected as a potent applicant for heavy metals detoxification.

• Serratia rubidaea NCTC12971 was characterized by its plant growth promoting traits and antifungal activity against Alternaria alternata.

摘要

使用微生物进行生物修复已成为对各种城市和工业废水进行解毒的创新有效工具。在这项研究中，我们首次使用具有多种植物生长促进特性的本土细菌Serratia rubidaea NCTC12971对磷酸盐处理废水 (PPWW) 的微生物解毒进行了研究。事实上，分离的菌株表现出有吸引力的磷酸盐溶解能力、铁载体产生以及吲哚乙酸 (IAA) 分泌能力。此外，该菌株对Alternaria alternata具有显着的抗真菌作用。在重金属浓度增加时对细菌生长的监测显示最小抑制浓度 (MIC) 为 8、6、3 和 3 mg L ^-1，分别为 Pb、Cd、Cu 和 Zn。Serratia rubidaea对 PPWW 的 10 天处理显着降低了其在电导率 (EC)、化学需氧量 (COD)、生化需氧量 (BOD ₅ ) 和总有机碳 (TOC)方面的盐度。在重金属去除方面，Pb、Cd、Cu 和 Zn 的解毒率分别为 94.4、91.5、85 和 66.5%。此外，PPWW 的生物处理降低了其对小扁豆 ( Lens culinaris )和鹰嘴豆 ( Cicer arietinum ) 种子萌发的植物毒性。因此，对于 PPWW，鹰嘴豆 ( Cicer arietinum ) 和小扁豆 ( Lens culinaris )的发芽指数 (GI)) 分别为 16.6 和 10%。同时，通过生物处理 (BTPPWW)，上述两种种子的 GI 显着增加至约 76.6%。这些结果加强了红色沙雷氏菌 NCTC12971在建立生物技术过程中的潜在用途，旨在最大限度地减少 PPWW 的有害影响及其作为植物生长促进细菌 (PGPB) 的用途。

• 强调

• 这项研究是调查土著细菌在突尼斯磷酸盐洗衣厂排放废水生物处理中的潜在用途的第一份报告。

• Serratia rubidaea NCTC12971 被选为重金属解毒的有力申请人。

• Serratia rubidaea NCTC12971 具有促进植物生长的特性和对链格孢菌的抗真菌活性。