Effect of Hydrogen Sulfide in Anoxic Marine Sediments on the Enzymatic Degradation of Particulate Proteins

Abstract

In Bolinao Bay, Pangasinan, there is a continuing accumulation of particulate proteins in the form of fish feeds on the coastal marine sediments because of extensive fish farming. Establishment of anoxia and production of H2S in sediments are some of the consequences. Hence, the influence of HS on the enzymatic degradation of particulate proteins is the study's main concern. Initially, a comparative study of sediments was conducted in Bolinao Bay to establish a possible association between HS and the enzymatic degradation of particulate proteins. Sediments near and distant from active fish cages were collected and characterized in terms of H2S presence, proteolytic activity. macroscopic appearance, protein content and redox potential. Proteolytic activity of sediments was determined in an enzyme assay using dyec-labeled scleroprotein as the enzyme substrate. This procedure measured largely the endoenzymatic degradation of solid protein into large dissolved molecules. The enzyme assay was conducted in two ways, one using the sediments directly and another using an enzyme culture fluid derived from an enriched culture of proteolytic bacteria, which were isolated from an oxic sediment sample. The data suggest that protein content had a strong negative correlation with redox potential; redox potential had a strong negative correlation with H2S presence; and H2S presence had a moderately negative correlation with proteolytic activity. Addition of HS to the enzyme culture fluid showed a direct inhibition on bacterial proteases. Proteolytic activity in anoxic sediments was significantly lower than the proteolytic activity in oxic sediments. However, the former was not significantly different from the proteolytic activity in anoxic sediments with H2S. These results indicate that though hydrogen sulfide directly inhibited bacterial proteases, total proteolytic activity was not inhibited when proteolytic enzymes were contained in sediments. Further, removal of H2S from natural sediments did not eliminate the inhibition of proteolytic activity.