Screening of exoenzymes for guar gum biodegradation in activated sludge and soil

Originally standardized biodegradation tests, designed for small molecules, are often considered inadequate for evaluating polymers, as they do not account for the crucial fragmentation step catalyzed by exoenzymes, which is essential for initiating the microbial degradation of polymers. In this study, the presence of EEs in the environment and their role in the biodegradation of guar gum, a WSP, were evaluated. A metagenomic shotgun approach assessed the abundance of genes encoding α-galactosidase and β-mannosidase in the Waste Water Treatment Plant (WWTP) and soil. Secondly, we employed sonication to release EEs, measured their activity, and evaluated the impact of their release on guar degradation using biodegradation tests. These findings indicated that genes encoding α-galactosidase and β-mannosidase were more abundant in the WWTP than in soil. A sonication protocol with a power density of 1 W/mL and a frequency of 20 kHz for 1 min (WWTP) and 2 min (soil) released EEs without significant cell lysis and significantly reduced the lag phase of guar-grafted acrylamide biodegradation from 8 to 5 days and decreased variability in native guar biodegradation by 10%. Our findings highlight the potential of WWTP and soil microbial communities to degrade guar gum by screening EEs and propose a new method for preparing the inoculum for WSPs biodegradation tests.