Evaluation of microbial triglyceride oil purification requirements for the CelTherm process: an efficient biochemical pathway to renewable fuels and chemicals.

CelTherm is a biochemical process to produce renewable fuels and chemicals from lignocellulosic biomass. The present study's objective was to determine the level of treatment/purity of the microbial triacylglyceride oil (TAG) necessary to facilitate fuel production. After a unique microbe aerobically synthesizes TAG from biomass-derived sugars, the microbes were harvested and dried then crude TAG was chemically extracted from the residual biomass. Some TAGs were further purified to hydrotreating process requirements. Both grades were then noncatalytically cracked into a petroleum-like intermediate characterized by gas chromatography. Experiments were repeated using refined soybean oil for comparison to previous studies. The products from crude microbial TAG cracking were then further refined into a jet fuel product. Fuel tests indicate that this jet fuel corresponds to specifications for JP-8 military turbine fuel. It was thus concluded that the crude microbial TAG is a suitable feedstock with no further purification required, demonstrating CelTherm's commercial potential.

Tertiary structure and characterization of a glycoside hydrolase family 44 endoglucanase from Clostridium acetobutylicum.

A gene encoding a glycoside hydrolase family 44 (GH44) protein from Clostridium acetobutylicum ATCC 824 was synthesized and transformed into Escherichia coli. The previously uncharacterized protein was expressed with a C-terminal His tag and purified by nickel-nitrilotriacetic acid affinity chromatography. Crystallization and X-ray diffraction to a 2.2-A resolution revealed a triose phosphate isomerase (TIM) barrel-like structure with additional Greek key and beta-sandwich folds, similar to other GH44 crystal structures. The enzyme hydrolyzes cellotetraose and larger cellooligosaccharides, yielding an unbalanced product distribution, including some glucose. It attacks carboxymethylcellulose and xylan at approximately the same rates. Its activity on carboxymethylcellulose is much higher than that of the isolated C. acetobutylicum cellulosome. It also extensively converts lichenan to oligosaccharides of intermediate size and attacks Avicel to a limited extent. The enzyme has an optimal temperature in a 10-min assay of 55 degrees C and an optimal pH of 5.0.