Isolation and characterization of two thermophilic Leptolyngbyaceae strains isolated from Huizhou area, China

Abstract:

[Background] With the increase of CO2 emissions and global temperatures, thermophilic cyanobacteria are considered as a promising group of organisms to convert CO2 into useful chemicals and biofuels at 45 °C or above. [Objective] This paper describes isolation and identification of thermophilic cyanobacteria collected from Huizhou area, and describes growth characteristics of two strains belonging to the family Leptolyngbyaceae to provide the basis for their subsequent application. [Methods] 16S rRNA gene and phycocyanin alpha chain (PhycoA) gene sequences were used in phylogenetic analysis to determine the taxonomical position of isolates from Huizhou area. Two strains PKUAC-GDTS1-24 and PKUAC-GDTS1-29 were observed morphologically and analyzed for major cellular components (ash, carbohydrate, lipid, protein and pigment). [Results] Twelve strains of thermophilic cyanobacteria were isolated, of which PKUAC-GDTS1-24 and PKUAC-GDTS1-29 were morphologically blue-green globular trichomes. Cells forming trichome formed dense clusters, that mostly attached to each other. Cellular contents of: ash, lipids, and protein were estimated to be 24.41%, 21.40%, 26.64%, respectively in PKUAC-GDTS1-24 strain. Carbohydrates were the major component of the strain at 36.42%. In another strain, PKUAC-GDTS1-29, the cellular contents of: ash, lipids, and protein contents were estimated to be 24.72%, 23.92%, 12.93%, respectively. The carbohydrates once again were the most abundant component with 28.46%. The contents of phycocyanin (PC) in PKUAC-GDTS1-24 and PKUAC-GDTS1-29 were 157.29 and 374.86 mg/g dry weight respectively, and the carotenoids were 65.13 and 18.87 mg/g dry weight, respectively. [Conclusion] Based on the phylogeny, PKUAC-GDTS1-24 and PKUAC-GDTS1-29 belong to the family Leptolyngbyaceae and cluster with many poorly described isolates. These isolates may be a potentially novel phylotype or a new genus of filamentous mildly thermophilic cyanobacteria that are present in the hot springs of Guangdong and Sichuan. The morphological features and cellular composition of both thermophilic Leptolynbya-like strains were similar. To our best knowledge, the two strains are the highest phycobiliprotein producers described to date from this cyanobacterial family, which could be used as potential strains for phycocyanin production, especially PKUAC-GDTS1-29.