Production of fermentable sugars from microalgae Chlorella pyrenoidosa

Lately, marine biomass got newly spotlighted as the next-generation biomass that could overcome the limit of plant biomass, and its use for biofuel is being focused and many applications are reported. Especially, study of biodiesel from microalgal lipids are well reported but utilization of carbohydrate are not represented which contains about 10-30% of carbohydrates. The purpose of this study was to produce fermentable sugars by using acid extraction and enzyme saccharification from Chlorella pyrenoidosa. First, the most effective reagent was investigated among the five reagents (hydrochloric acid, nitric acid, phosphoric acid, peracetic acid and sulfuric acid). The hydrochloric acid showed the highest sugar extration and two factors of reaction condition were investigated solid/liquid ratio and acid concentration. Optimal conditions were found to be 2% of hydrochloric acid and 100 g/L of solid/liquid ratio, respectively. Under these conditions, the sugar recovery showed about 90% from C. pyrenoidosa. Second, for enzyme saccharification, pretreatment was conducted with 1% alkaline solution (ammonia, sodium hydroxide), and hydrolysis was performed by using various enzymes. Combination of amylase with C-tec II showed the highest glucose conversion and enzyme activities used were 30 amyloglucosidase unit (AGU) of amylase and 60 filter paper unit (FPU) of C-tec II. Overall, the sodium hydroxide treatment was more effective in cell wall destruction at the same condition and conversion was 2.5 fold increased comparing with untreated C. pyrenoidosa.