TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (disclosed): The modified photosynthetic microorganism is prepared by standard recombinant methods. Preferred Microorganism: The modified photosynthetic microorganism is Cyanobacteria. The enzymes comprise diacylglycerol acyltransferase (DGAT), phosphatidate phosphatase, acetyl-CoA carboxylase (ACCase), or their fragment or variant. The DGAT is Acinetobacter DGAT, Streptomyces DGAT or Alcanivorax DGAT. The polynucleotide is exogenous to the photosynthetic microorganism's native genome, present in one or more expression constructs, or codon-optimized for expression in a Cyanobacterium. The Cyanobacterium is chosen from Synechococcus elongatus strain PCC 7942, salt tolerant variant of S.elongatus strain PCC 7942, Synechococcus strain PCC 7002 and Synechocystis strain PCC 6803. The photosynthetic microorganism comprises polynucleotide encoding one or more enzymes associated with lipid biosynthesis, where the enzymes are chosen from Saccharomyces cerevisiae acetyl-CoA carboxylase (yAcc1), Acinetobacter baylii strain ADP1 diacylglycerol acyltransferase (AtfA) and Saccharomyces cerevisiae phosphatidate phosphatase (yPah1), the polynucleotides are codon-optimized for expression in Cyanobacteria, the expression of the enzyme is regulated by one or more inducible promoters, and the photosynthetic microorganism is S.elongatus PCC7942. EXAMPLE - Microorganisms such as Acinetobacter baylii strain ADP1 having capability of synthesizing diacylglycerol acyltransferase (DGAT) (AtfA or ADP1-DGAT) were obtained. Then ADP1-DGAT nucleotide sequence was synthesized and codon optimized for Synechococcus elongatus strain PCC 7942 expression using DNA2.0, introduced in a plasmid, subcloned using established molecular biology techniques into the isopropyl- beta -D-thio-galactoside (IPTG)-inducible vector pAM2991trc, and recombined into neutral site 1 (NS1) of S.elongatus strain PCC 7942. Colonies were selected from BG11-spec/strep plates, recultured for isolation, and tested by PCR for positive colonies. Inducible transcription of the gene was verified by real-time PCR. Microorganisms such as Saccharomyces cerevisiae having capability of synthesizing three phosphatidate phosphatases (Pah1) were obtained, the Pah1 nucleotide sequence was synthesized and codon optimized for S.elongatus strain PCC 7942 expression using DNA2.0, introduced in a plasmid, subcloned using established molecular biology techniques into the IPTG-inducible vector pAM2991trc, and recombined into NS1 of S.elongatus strain PCC 7942. Colonies were selected from BG11-spec/strep plates, recultured for isolation, and tested by PCR for positive colonies. The ADP1-DGAT expressing strain (ADP1-DGAT subcloned into IPTG-inducible vector pAM1579trc-kanamycin, which recombined in NS2) was transformed with the construct containing Pah1 from NS1 and transformant was selected on plates containing kanamycin, streptomycin and spectinomycin to obtain S.elongatus strain PCC 7942 expressing both the ADP1-DGAT and Pah1 genes.