TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (Claimed): The modified photosynthetic microorganism is produced by introducing a polynucleotide encoding a lipase, or its fragment or variant into photosynthetic microorganism, where the modified photosynthetic microorganism accumulates increased amount of cellular lipid when compared to corresponding wild-type photosynthetic microorganism. The method (M1) further involves introducing one or more polynucleotides encoding one or more enzymes associated with fatty acid, lipid and/or triglyceride biosynthesis into the photosynthetic microorganism. Preferred Microorganism: The microorganism further comprises one or more introduced polynucleotides encoding one or more enzymes associated with fatty acid, lipid, and/or triglyceride biosynthesis, reduced expression of one or more genes of glycogen biosynthesis or storage pathway as compared to the wild-type photosynthetic microorganism, or one or more endogenous or introduced polynucleotides encoding protein of glycogen breakdown pathway. The modified photosynthetic microorganism expresses an amount of lipase optimized for continuous high level fatty acid production without substantial toxicity to the modified photosynthetic microorganism, where the expression amount is regulated by promoter operably linked to the introduced polynucleotide and/or copy number of the introduced polynucleotide. Preferred Components: The lipase is phospholipase or lysophospholipase. The lipase is chosen from cytoplasmic localized Escherichia coli lysophospholipase, periplasmic-localized E.coli lysophospholipase, Patatin 1 protein, acyl-coenzyme A (CoA) thioesterase, acyl-acyl carrier protein (ACP) thioesterase, acyl-CoA/acyl-ACP thioesterase, cytoplasmic localized E.coli TesA, periplasmic-localized E.coli acyl-CoA/ACP thioesterase, periplasmic-localized E.coli TesA, E.coli TesB, and FatB acyl-ACP thioesterase. The lipase has both thioesterase activity and lysophospholipase activity, thioesterase activity but not lysophospholipase activity, or acyl-ACP thioesterase activity but not acyl-CoA thioesterase activity. Preferred Enzyme: The enzyme comprises diacylglycerol acyltransferase (DGAT), phosphatidate phosphatase, or acetyl-CoA carboxylase (ACCase). Preferred Polynucleotide: The introduced polynucleotide is present in one or more expression construct. The introduced polynucleotide encoding lipase is present in expression construct containing weak promoter under non-induced conditions. EXAMPLE - Lysophospholipase L1 and L2 encoded by pldC(teas) and pldB gene obtained from Escherichia coli was introduced into arabinose or isopropyl- beta -D-thiogalactopyranoside (IPTG)-inducible vectors and was recombined into neutral sites of Synechococcus elongatus PCC 7942. Colonies were selected from BG11-spec/strep or BG11-kan and tested by PCR for positive colonies.