OPTIMIZATION OF MOLASSES WITH DIFFERENT CONCENTRATIONS AS ORGANIC CARBON SOURCE FOR MIXOTROPHIC CULTIVATION OF CHLORELLA VULGARIS

• Main Author: Afriani, Atika
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/62289
• Institution: Institut Teknologi Bandung

Organic carbon in the culture medium plays an important role in increasing the biomass productivity and lipid content of Chlorella vulgaris under mixotrophic condition. Consequently, there will be increasing the cost of culture medium to fulfill the needs of organic carbon sources such as glucose or acetic acid which are generally used. Therefore, substitution of molasses as a potential organic carbon source that is cheap, easily obtained and its availability effectively improves biomass production. In addition, environmental factors could affect cell growth and biomass accumulation. Nutrient limiting stress such as sulphur deprivation will encourage higher lipid accumulation. Therefore, this study aimed to determine the best molasses concentration as organic carbon source in the mixotrophic cultivation of C. vulgaris on biomass production, growth rate, pH during growth period and biochemical composition. In this study, the growth of C. vulgaris was optimized by adding molasses in different concentration (500, 1000, 1500, 2000 ppm) as organic carbon whereas NaHCO3 1000 ppm as inorganic carbon. 10% inoculum (v/v) was inoculated in Bold.s Basal Medium (BBM) deprived sulphur and standard BBM as a control then incubated for 14 days at room temperature (26±0,5 oC), initial pH 6,9, white light intensity 1500 lux, photoperiod 12:12 and agitation 150 rpm. Biomass concentration, growth rate, changes in pH, chlorophyll, lipids and protein content were carried out based on variations of molasses concentration. Biomass concentration was determined by spectrophotometric method by measuring the absorbance at ? = 680 nm and cell density by haemocytometer. Analysis of chlorophyll content referred to the Parsons and Strickand method (1973), lipid content by the Bligh and Dyer method (1965) and protein content by the Bradford method (1976). Growth profile of C. vulgaris showed higher cell density and specific growth rate under mixotrophic cultivation. Based on these results, the best inoculum was reached at 5,5th day with growth rate 0,430±0,111 day-1. Molasses concentration with the ratio Cinorganic:Corganic = 1:1 (1000 ppm), 1:1,5 (1500 ppm) and 1:2 (2000 ppm) was able to increase biomass production (p<0,05) under mixotrophic growth. The highest specific growth rate about 0,504±0,010 day - 1 with doubling time1,38±0,01 days is obtained by adding molasses 1000 ppm. The biomass of molasses 2000 ppm added was the highest cell density 8,43 x 107 sel/ml and dry cell weight (DCW) 1,888±0,049 g/l (p<0,05). Besides, molasses increased the lipid content (p<0,05) whereas the chlorophyll a and protein content were slightly lower than autotrophic growth. The highest value of chlorophyll a, lipid and protein content was obtained at the added molasses 2000 ppm, namely 3,18±0,01 mg/l, 27,3±0,4% and 37,3±0,9% respectively. In addition, molasses as organic carbon source caused the pH value fluctuated under mixotrophic growth. pH range of 6,8-8-3 was optimum for C. vulgaris growth under mixotrophic condition. Culture medium composition and utilization of the available carbon source affected pH value during cultivation. Thus, molasses can be used as an alternative carbon source for mixotrophic cultivation on laboratory.