An engineered polysaccharide lyase to combat harmful algal blooms

Abstract

A growing global population and industrialization have come at the cost of induced climate change and pollution of natural resources, resulting in formation of toxic algal blooms in fresh water sources. In the US alone, these blooms cost an estimated $1.5 billion dollars each year to remediate. Current methods to combat such blooms such as copper sulfate treatment are expensive, ineffective, and environmentally toxic, motivating development of biochemical algaecides as green alternatives. Our previous research led to identification of mutant polysaccharide lyase (PL) enzyme H208F derived from Stenotrophomonas maltophilia Smlt2602 (WT), which displays increased activity on the polysaccharide polyglucuronic acid. Polyglucuronic acid is a major component of the algal cell wall. This study focused on applying the two enzymes to a common bloom-forming, toxin-producing algae, Microcystis aeruginosa. We hypothesized the 2 enzymes would kill algae through disrupting the cell wall, with H208F displaying a higher killing efficacy over WT. A fluorescence assay in conjunction with live/dead staining was used to quantify killing of algae treated with each enzyme. SEM analysis was used to observe cell wall morphology in order to verify the killing mechanism. The mutant H208F was confirmed as having potential application as a biochemical, enzymatic algaecide with a 17% greater algicidal efficacy than the WT. SEM images revealed deformities in the algal cell wall, confirming the purported mechanism.