Characterization of a Korean Domestic Cyanobacterium Limnothrix sp. KNUA012 for Biofuel Feedstock

A filamentous cyanobacterium, Limnothrix sp. KNUA012, was axenically isolated from a freshwater bloom sample in Lake Hapcheon, Hapcheon-gun, Gyeongsangnam-do, Korea. Its morphological and molecular characteristics led to identification of the isolate as a member of the genus Limnothrix. Maximal growth was attained when the culture was incubated at 25°C. Analysis of its lipid composition revealed that strain KNUA012 could autotrophically synthesize alkanes, such as pentadecane (C 15 H 32 ) and heptadecane (C 17 H 36 ), which can be directly used as fuel without requiring a transesterification step. Two genes involved in alkane biosynthesis－an acyl-acyl carrier protein reductase and an aldehyde decarbonylase－were present in this cyanobacterium. Some common algal biodiesel constituents－myristoleic acid (C 14:1 ), palmitic acid (C 16:0 ), and palmitoleic acid (C 16:1 )－were produced by strain KNUA012 as its major fatty acids. A proximate analysis showed that the volatile matter content was 86.0% and an ultimate analysis indicated that the higher heating value was 19.8 MJ kg -1 . The isolate also autotrophically produced 21.4 mg g -1 phycocyanin－a high-value antioxidant compound. Therefore, Limnothrix sp. KNUA012 appears to show promise for application in cost-effective production of microalga-based biofuels and biomass feedstock over crop plants.