Microalgae biomass contains cellulose which can be converted into reducing sugar by enzymatic hydrolysis. The reducing sugar later can be fermented to produce bioethanol. The higher biomass productivity, then the higher sugar produced by enzymatic hydrolysis. This study investigated the optimization parameters of Chlorella sp. cultivation to produce high biomass productivity and the optimal conversion parameters to produce reducing sugar by the cellulase hydrolysis of Chlorella sp.
At some cultivation batches where the growth was fast, specific growth rate of Chlorella sp. has two regions. The highest specific growth rate of the first region was 0.50/ day at Batch 7, but the highest one of the second region was 0.18/day at Batch 8. The highest cell density was 9.69 g/L which was produced from Batch 8. Both Batch 7 and 8 were run under 2 L volume, with 20% inoculums, 0.1% nutrient, 0.1% urea, 0.01% vitamin, 2 L/min air flowrate under light intensity up to 252 µmol/(m2．s). Batch 7 was added with 1% CO2 every other day and stirring rate was 120 rpm, while Batch 8 was added with 1% CO2 continuously and stirring rate was 250 rpm.
The hydrolysis of concentrated algae with 30 mg cellulase enzyme in 2 mL pH 6.0 phosphate buffer under 60°C, produce 5.67 g/L glucose after 8 hours. The hydrolysis of 25 mg wet biomass of Chlorella sp. with 10 mg cellulase enzyme in 2 mL pH 6.0 phosphate buffer under 55°C, produce 3.07 g/L glucose after 58 hours hydrolysis time.

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