Thesis (M.Sc.)--Chulalongkorn University, 2013

Mycosporine-like amino acid (MAA) is secondary metabolite. It has specific ultraviolet B absorption in the range between 310-362 nm. Primary function of MAA is to protect microorganism from harmful effects of UV-B. There have been reported that MAA can be synthesized in high amount under stress condition. Thus far, biosynthetic pathway for MAA has only studied in filamentous cyanobacteria; Anabaena variabilis ATCC 29413 and Nostoc punctiforme ATCC 29133. In these cyanobacteria, a cluster of genes for MAA biosynthesis comprises of Ava_3858/NpR5600, Ava_3857/NpR5599, Ava_3856/NpR5598, and Ava_3855/NpF5597, respectively. In this research, we employed a halotolerant cyanobacterium Aphanothece halophytica for the study MAA induction, biosynthesis including metabolic engineering approaches. Analysis and identification of MAA were examined by High Performance Liquid Chromatography and Amino Acid Analysis. We have identified that MAA accumulation in A. halophytica is Mycosporine-2-glycine. Furthermore, biosynthetic gene cluster for MAA from A. halophytica was expressed into E. coli and Synechococcus sp. PCC 7942. MAA was highly induced under salt stress condition in both expressing cells. In our tested conditions, E. coli expressing cells could produce and accumulate MAA with maximum yield 85.20 ± 2.69 µmol/g DW.