Enhancing hexavalent chromium stable reduction via sodium alginate encapsulation of newly isolated fungal and bacterial consortia

Chromium [Cr(VI)]-induced soil pollution is a serious environmental threat. Bioremediation utilizes specific microbes capable of transforming Cr(VI) into the less toxic Cr(III), however, microbial efficacy can be inhibited by elevated pollutant concentrations and competition from indigenous microbial communities. Thus, this study explored the potential of single and multi-domain microbial consortia encapsulated in alginate to overcome these shortcomings. The results revealed that (i) fungal treatments demonstrated an elevated tolerance and reduction ability for Cr(VI) compared to bacterial treatments; (ii) combined application of fungi and bacteria was more effective in degrading Cr(VI) in soil compared to the individual treatments; (iii) microbial encapsulation improved microbial response to Cr(VI) toxicity thereby increasing their lifespan and Cr(VI) degrading ability; (iv) microbial consortia significantly decreased soil pH, electrical conductivity, and redox potential while simultaneously increasing soil enzyme activities (urease, sucrase, phosphatase, catalase, and laccase); and (v) The improved tolerance in the inoculated treatment resulted in increased microbial diversity and a substantial variation in microbial community structures, with 10,753 bacterial and 2697 fungal amplicon sequence variants identified across the treatment groups. This study underscores the critical importance of microbial diversity in bioremediation, emphasizing that encapsulation with the right material could improve the effectiveness of environmental remediation strategies.