Enzyme production by a fungoid marine protist, Thraustochytrium striatum

Abstract

Thraustochytrium striatum is a fungoid marine protist and was shown to be a promising enzyme producer for potential industrial applications. This research aimed at studying extracellular enzymes secreted by T. striatum under different conditions with specific objectives to qualitatively identify enzymes, quantify the cell growth and enzyme production, correlate enzyme production with extracellular polymeric substances (EPS), and examine the induction of enzyme by polysaccharide substrates. The qualitative analysis showed that T. striatum can produce at least seven extracellular enzymes including lipase and six polysaccharases (i.e., amylase, CMCase, xylanase, chitinase, pectinase, and κ-carrageenase). The carbon and nitrogen concentrations and salinity significantly affected the kinetics of enzyme production. T. striatum produced decent amount of polysaccharases at all conditions, but negligible lipase. Amylase was the predominant enzyme and reached the highest activity of 750 U/L with glucose = 30 g/L, nitrogen source = 6 g/L and salinity = 100% sea water. Enzymes appeared to correlate with the production and monosaccharide composition of EPS. Enzyme-specific polysaccharide substrates including starch, CMC, xylan, κ-carrageenan, pectin, and chitin did not induce the production of corresponding enzymes by T. striatum while carbon starvation condition resulted in comparable enzyme activities, which indicated that enzymes from T. striatum were constitutive.