Enzymatic exposure impacts microbial diversity and reduces biovolume of reverse osmosis membrane-associated biofilms

Biofilms are known for their persistence and resilience, which reduce the effectiveness of conventional cleaning strategies for industrial processing membranes. A sustainable alternative is to utilize matrix-degrading enzymes to reduce biofilm formation and remove cells. In this study, we investigated the impact of an enzyme mixture on the structure, diversity, and composition of biofilm communities formed on reverse osmosis (RO) membranes using dairy industry wastewater. Biofilms were grown under dynamic flow conditions in a lab-scale RO fouling monitor to mimic industrial operations. Microscopic imaging revealed a substantial reduction in microbial biovolume after 4 and 24 h of enzyme treatment, while molecular analyses showed significant decreases in bacterial (62.39 %) and fungal (79.73 %) gene copy numbers, particularly after 24 h. Bacterial communities demonstrated high diversity and subtle changes in the relative abundance of specific genera, whereas fungal communities remained relatively uniform. Despite these variations, the enzyme treatment induced a general decrease in the normalized gene copy numbers of bacterial genera. The treatment notably reduced bacterial alpha diversity, primarily attributed to decreased richness, while fungal diversity showed no significant changes. Extended enzyme exposure proved essential for effectively disrupting biofilm and reducing bacterial genera abundances. However, certain genera, such as Raoultella and Lactococcus, were less sensitive to enzymatic degradation, highlighting the need for targeted strategies to address resilient taxa.