RESUMO
Staphylococcus sp. WL1 lipase (LipFWS) was investigated for methanolysis of crude palm oil (CPO) at moderate temperatures. Experiments were conducted in the following order: searching for the suitable bacterium for producing lipase from activated sludge, sequencing lipase gene, identifying lipase activity, then synthesising CPO biodiesel using the enzyme. From bacterial screening, one isolated specimen which consistently showed the highest extracellular lipase activity was identified as Staphylococcus sp. WL1 possessing lipFWS (lipase gene of 2,244 bp). The LipFWS deduced was a protein of 747 amino acid residues containing an α/ß hydrolase core domain with predicted triad catalytic residues to be Ser474, His704 and Asp665. Optimal conditions for the LipFWS activity were found to be at 55 °C and pH 7.0 (in phosphate buffer but not in Tris buffer). The lipase had a K(M) of 0.75 mM and a V(max) of 0.33 mMmin(-1) on p-nitrophenyl palmitate substrate. The lyophilised crude LipFWS performed as good as the commonly used catalyst potassium hydroxide for methanolysis of CPO. ESI-IT-MS spectra indicated that the CPO was converted into biodiesel, suggesting that free LipFWS is a worthy alternative for CPO biodiesel synthesis.
Assuntos
Proteínas de Bactérias/química , Lipase/química , Metano/química , Óleos de Plantas/metabolismo , Staphylococcus/química , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Sequência de Bases , Biocatálise , Biocombustíveis , Concentração de Íons de Hidrogênio , Cinética , Lipase/genética , Lipase/isolamento & purificação , Dados de Sequência Molecular , Fases de Leitura Aberta , Óleo de Palmeira , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Análise de Sequência de DNA , Esgotos/microbiologia , Staphylococcus/enzimologia , TemperaturaRESUMO
To understand the potential of cultivating tropical marine diatom Thalassiosira sp. to produce biofuel, biodiesel product properties and growth characteristics of Thalassiosira sp. in three different media were investigated. After medium evaluation, significant Thalassiosira sp. cell growth was observed in both Walne and enriched seawater media, but not in plain seawater medium. The microalgae grew well in alkaline condition (pH range of 8.0-8.8). The average biomass density cultured in Walne and enriched seawater media on the 6th day was 4.36 and 2.50 g L(-1), respectively. Based on ESI-IT-MS spectra, the TAGs of algal oil were identified as POP, POO, and SOO, and the FAMEs as oleic acid methyl ester. The oil productivity of Thalassiosira sp. cultured in Walne and enriched seawater media were 150 and 290 µL L(-1) d(-1), respectively. The density and kinematic viscosity of Thalassiosira sp. biodiesel were 0.857 g mL(-1) and 1.151 mm(2) s(-1).
