Sarocladium strictum lipase (LipSs) produced using crude glycerol as sole carbon source: A promising enzyme for biodiesel production

Abstract

The production of biodiesel (fatty acid methyl esters), an environmentally safe next-generation biofuel, using a lipase from Sarocladium strictum and glycerol (a biodiesel by-product) as sole carbon source, was investigated. The fungus S. strictum showed maximum lipase production when grown in crude glycerol (3.13 U/mg protein) with 168 h of growth. Different concentrations of crude glycerol as carbon source were tested and concentrations ranging from 0.5 to 4% were completely consumed (100%) by the S. strictum . The lipase from S. strictum was purified (24.4-fold) with a specific activity of 73.2 U/mg protein showing a molecular weight of 52 kDa. The effects of pH and temperature in the lipase activity were evaluated showing optimal activity at pH 5.0 and 40 °C, respectively. Lipase hydrolyzed different substrates and exhibited better activity on p -nitrophenyl octanoate (30.68 U/mg protein). The detergents Triton X-100 and Tween 80 at concentration of 0.1% (v/v) increased the lipase activity by 10.45 and 8.55%, respectively. The lipase maintained 80% residual activity in the presence of methanol (1:1, v/v) after 24 h of incubation. In concentrations ranging from 1 to 5% of methanol, showed activity above 90%, maintaining 70% activity at 10% concentration. Gas chromatography mass spectrometry (GC–MS) analysis confirmed biodiesel production with soybean and sunflower oil by lipase with a conversion rate of approximately 65 and 85%, respectively. Therefore, the lipase was efficient in the conversion of low-cost plant oil to high-value biodiesel. • Production of lipase by S. strictum using crude glycerol, a by-product of biodiesel as carbon source. • Conversion of low-cost plant oil to high-valued biodiesel by a fungal lipase. • Biodiesel production using purified lipase and detected by GC analysis.