ST3-05: Enzymatic hydrolysis of algal biomass for enhancement of lipid extraction and carbohydrate utilization

Commercial enzyme mixtures (Viscozyme (Mix-E)), crude enzymes obtained from cell homogenization (Chl-E) and viral lysate (Vir-E) were selected as candidate enzyme mixtures for treatment of Chlorella cell walls and live cells in order to facilitate the collection of lipid or starch for bioproducts.  The cell wall of Chlorella minutissima UTEX 2341 was relatively more sensitive to all tested enzymes in comparison to the cell walls of Chlorella vulgaris UTEX 259 and Chlorella sorokiniana UTEX 2805.  Most of the carbohydrates released by enzymatic digestion were in polymer form; only a small amount of reducing sugar was present in the UTEX 2341 cell wall hydrolysate.  For enzymatic treatment of live cultures, full factorial experiments were designed to investigate the effects of enzyme mixtures on enhancement of lipid extraction, starch hydrolysis, and release of carbohydrates.  The results showed that different strains of Chlorella had different susceptibilities to the enzyme combinations.  All three enzyme mixtures showed significant effects on carbohydrate release for Chlorella UTEX 259 and 2805 but not for Chlorella UTEX 2341.  The release of carbohydrate did not always correlate to an enhancement of lipid extraction and starch hydrolysis.   Viscozyme had a significant effect on enhancement of starch hydrolysis for all three tested Chlorella strains, but it only improved lipid extraction for Chlorella UTEX 2805.  Virus crude lysin also enhanced lipid extraction for Chlorella UTEX 259, but not the other two strains.  For Chlorella UTEX 2341, lipid extraction and starch hydrolysis were not affected by most of the enzyme treatments.