Publication:

Fundamental study of the structure glycerol-3-phosphate acyltransferase (GPAT) protein from chlorella sp. on understanding of lipid synthesis

Lipid content and type of fatty acids produced by microalgae are the main factors in determining the potential use of microalgae biomass due to the fact that microalgae lipid has high potential applications food, biofuels and pharmaceutical industries. A lot of research has been perfomed focusing on all aspects of microalgae lipid production including the basic research on triacylglycerol (TAG) biosynthesis pathway. Glycerol-3-phosphate acyltransferase (GPAT) is the first enzyme that catalyzes the TAG synthesis. Thus targeting GPAT can be considered as powerful strategy for lipid enhancement. This study aims to determine biomass, lipid content and fatty acid composition from freshwater and marine Chlorella vulgaris (C. vulgaris) at four different salinity profile. The information on GPAT sequence is used to aid in predicting 3D structure of GPAT protein structure using homology modeling technique. Marine C. vulgaris were cultured in four different salinity which were 10, 20, 30 and 40 ppt in Conway media while freshwater C. vulgaris was cultured in Bold Basal media. All cultures were grown and harvested during early stationary phase for biomass yield, total lipid content and fatty acid profiling analysis. The highest biomass was produced by 30 ppt marine C. vulgaris with 0.1650 ± 0.012 g/L and the lowest was 10 ppt salinity with 0.0793 ± 0.012 g/L. The maximum lipid produced can reach up to 23% by 30 and 40 ppt and the minimum was 14.7 % by 10 ppt. Lipid profiling showed that, palmitic acid and linolenic acid were present on all cultures. Marine microalgae at 40 ppt culture has saturated fatty acid (SFA) as the highest fatty acid while polyunsaturated fatty acid (PUFA) was the major compound for freshwater. In this study, 3D structure of GPAT was predicted by using GPAT protein sequence from Chlorella sorokiniana and Cucurbita moschata as the template. The monomer consists of 14α helices and 8β sheets. In conclusion, different salinity affect the presence of fatty acid composition in C. vulgaris. In addition, the structural study obtained from this study also may provide useful information for engineering GPAT protein to increase the production of lipid in microalgae.