Enzymatic conversion of acid oils to biodiesel

Monitoring Enzymatic Hydroesterification of Low-Cost Feedstocks by Fourier Transform InfraRed Spectroscopy

Enzymatic hydroesterification is a heterogeneous catalyzed process suitable for the conversion of low-cost feedstocks in biodiesel production, namely, because of its tolerance to high free fatty acid contents. The current study describes the use of Fourier transform infrared spectroscopy (FTIR) to monitor biodiesel production using enzymatic hydroesterification and, as raw materials, acid oil from soapstock and olive pomace oil. Acid oil (~34 wt.% FFA) and olive pomace oil (~50 wt.% FFA) were first hydrolyzed (35 °C, 24 h, 200 rpm, 3 wt.% of lipase from Thermomyces lanuginosus, and 1:0.5 water:oil ratio, w:w), and then enzymatic esterification was performed (35 °C, 7 h, 200 rpm, 2 wt.% of lipase from Thermomyces lanuginosus, and 2:1 molar ratio of methanol to acid). FTIR analyses were conducted on the products using a Jasco FT/IR-4100 with a scanning range of 4000–650 cm−1 at 4 cm−1 spectral resolution and 54 scans. For free fatty acid (FFA) quantification, the C=O band at 1708 cm–1 was used, corresponding to the carboxylic acid, whereas for fatty acid methyl ester (FAME) quantification, the peak corresponding to C=O at 1746 cm−1 was considered, which corresponded to the ester. The results were calibrated using volumetric titration and gas chromatography analyses, concerning FFA and FAME quantification, respectively. The best conditions for analysis were determined, and a calibration method was established. FTIR has shown to be a simple, fast, and clean technique suitable to monitor hydroesterification of low-cost feedstocks.

Creating an Efficient Methanol-Stable Biocatalyst by Protein and Immobilization Engineering Steps towards Efficient Biosynthesis of Biodiesel

Two ternary sol-gel matrices, an octyltriethoxysilane-based aliphatic matrix and a phenyltriethoxysilane (PTEOS)-based aromatic matrix, were used to immobilize a methanol-stable variant of lipase from Geobacillus stearothermophilus T6 for the synthesis of biodiesel from waste oil. Superior thermal stability of the mutant versus the wildtype in methanol was confirmed by intrinsic protein fluorescence measurements. The influence of skim milk and soluble E. coli lysate proteins as bulking and stabilizing agents in conjunction with sol-gel entrapment were investigated. E. coli lysate proteins were better stabilizing agents of the purified lipase mutant than skim milk, as evidenced by reverse engineering of the aromatic-based system. This was also shown for commercial Candida antarctica lipase B (CaLB) and Thermomyces lanuginosus lipase (TLL). Uniform, dense, and nonaggregated particles imaged by scanning electron microscopy and a small particle size of 13 μm pertaining to the system comprising PTEOS and E. coli lysate proteins correlated well with high esterification activity. Combining protein and immobilization engineering resulted in a durable biocatalyst with efficient recycling ability and high biodiesel conversion rates.