PRELIMINARY STUDY OF CONVERSION OF BIOMASS MICROALGAE Chlorella sp. INTO BIOETHANOL

• Main Author: RIDHANI RAHMANIYAH (NIM : 20510011); Pembimbing : Zeily Nurachman D.Sc, WIWIT
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/17594
• Institution: Institut Teknologi Bandung

World energy demand increases together with the increase of population and industry. However, energy supplies in particular from fossil fuel remain unchanged. Oxidation of fuels also produces carbon dioxide (CO2) resulting <br /> <br /> <br /> greenhouse effects. Efforts to search novel energy sources that are renewable, sustainable, efficient, inexpensive, and environmentally friendly, for example bioethanol are needed. Since microalgae produce carbohydrates in the form of starch, algal biomass can be used for bioethanol feedstock. The use of microalgae biomass for bioethanol feedstock show many advantages: grow rapidly, tolerate in <br /> <br /> <br /> high CO2 concentration, accumulate large amount of carbohydrates, and do not compete with food, agriculture and residential land. The present study focused on <br /> <br /> <br /> conversion of Chlorella sp. biomass to bioethanol. Chlorella sp. cells were cultured on three different lighting conditions: under fluorescent lamps (10,000 <br /> <br /> <br /> lux) with photoperiods of 12 h and 24 h a day, as well as direct sunlight exposure. The results showed that maximum Chlorella sp. cell density (21.74 x 106 cells/mL) was obtained from the culture on day 17th and illuminated under <br /> <br /> <br /> fluorescent lamps with photoperiods of 12 h a day. Meanwhile, Chlorella sp. cell density under direct sunlight exposure and continuous fluorescent lamp were 21.47 × 106 cells/mL (harvested on day 12nd) and 16.68 × 106 cells/mL (on day 6th), respectively. Carbohydrate content obtained from microalgae biomass cultured under fluorescent lamps with photoperiods of 12 h and 24 h a day, as well as direct sunlight exposure was 33.73, 23.03, and 27.15% (w/w), <br /> <br /> <br /> respectively. The culture condition of Chlorella sp. under fluorescent lamps with photoperiods of 12 h a day to produce high carbohydrate concentration was used for biomass production. To hydrolyze carbohydrates, 5% (w/v) biomass of Chlorella sp. was pretreated with 1M HCl and heated in boiling water bath for 2 h. The yield of hydrolysis products determined by HPLC using a refractive index detector was 23.4% (w/w) glucose and 11.8% (w/w) xylose. After pH adjustment to 4.5, the hydrolysate was fermented using Saccharomyces cerevisiae for 72 h at <br /> <br /> <br /> 30 oC, and bioethanol product was determined by HPLC. The yield of ethanol obtained from the fermentation was 16.2% (w/w). These results suggest that Chlorella sp. biomass can be used for bioethanol feedstock.