Application of an optimized pectinolytic bacterial consortium to boost hemp water retting

The increasing interest on natural and ecological solutions, driven by environmental concerns and the growing popularity of natural materials, accelerated research into sustainable fibers. Hemp fibers are particularly notable due to its low environmental impact with respect to petroleum-based synthetic fibers, high production potential, and versatility. Retting is a crucial treatment of hemp that is necessary for the conversion of crop into processed fiber enhancing its availability and quality. To improve water retting processes of hemp stems, a selected pectinolytic bacterial consortium which included Pseudarthrobacter equi P61P, Bacillus subtilis A87P, Stenotrophomonas pictorum E711P, and Krasilnikoviella muralis E64P, was employed in a laboratory-scale experiment. A polyphasic approach combining selective and differential cultivation with enzymatic and metagenomic techniques allowed to monitor the dynamics and activity of microbial populations for evaluating the progress of the retting process. The quality of the cellulose fibers was assessed over 28 days based on parameters such as color, and dry matter percentage. The results demonstrated the effectiveness of the bacterial consortium to accelerate the maceration process and improve some qualitative characteristics. In fact, optimal maceration times were found to be between 7 and 14 days, corresponding to the high pectinolytic activity (0.57 ± 0.18 U mL −1) in an alkaline environment (pH from 6.0 to 9.7), reaching high-quality fibers without compromising yield (23.68 ± 0.81 % dry matter). Additionally, the study indicated the possibility to simplify the consortium comprising only Bacillus subtilis A87P and Stenotrophomonas pictorum E711P without compromising the optimization of the process and the standardization of hemp fiber quality.