• Energy Research

To achieve high time-space efficiency for sophorolipid production with yeast Candida bombicola, a strategy of high cell density fermentation was employed. The approach consisted of two sequential stages: (1) the optimization of the carbon source and the nutrient concentration to achieve the maximal cell density and (2) the computer-aided adjustment of physical parameters and the controlled feeding of substrates for enhanced volumetric productivity. Both stages have been successfully implemented in a 10-L fermenter, where up to 80 g dry cell weight/L was obtained and a remarkably high volumetric productivity (> 200 g isolated sophorolipids/L/day) was achieved. Both the biomass and volumetric productivity were markedly higher than previously reported. Specifically, the high productivity of sophorolipids could be attained on a very short time scale (24 h), highlighting the industrial potential of the platform developed in this work.

AbstractFatty acid methyl esters (FAME) were the first fatty acid esters to be introduced for use as biodiesel. However, there is a growing interest in the use of fatty acid ethyl esters (FAEE) in biodiesel. Both FAME and FAEE have their own unique advantages and disadvantages. These differences are ultimately attributable to the structural differences imparted by the alcohols used in their production. Sources of reactants as well as their safety issues, are a focus of this review. Also reviewed are the comparative characteristics and properties of both biodiesel types in terms of physicochemical features and performance. Processing requirements, reaction times and molar ratios of alcohol to oil, together with problems and drawbacks, are discussed. Recent developments on improving the yield of biodiesel, include mixing methanol and ethanol in the same reaction with ethanol acting as a co‐solvent, and enzymatic methanolysis and ethanolysis are also highlighted.

To develop an efficient green extraction approach for recovery of bioactive compounds from natural plants, we examined the potential of pressurized liquid extraction (PLE) of ginger (Zingiber officinale Roscoe) with bioethanol/water as solvents. The advantages of PLE over other extraction approaches, in addition to reduced time/solvent cost, the extract of PLE showed a distinct constituent profile from that of Soxhlet extraction, with significantly improved recovery of diarylheptanoids, etc. Among the pure solvents tested for PLE, bioethanol yield the highest efficiency for recovering most constituents of gingerol-related compounds; while for a broad concentration spectrum of ethanol aqueous solutions, 70% ethanol gave the best performance in terms of yield of total extract, complete constituent profile and recovery of most gingerol-related components. PLE with 70% bioethanol operated at 1500 psi and 100 °C for 20 min (static extraction time: 5 min) is recommended as optimized extraction conditions, achieving 106.8%, 109.3% and 108.0% yield of [6]-, [8]- and [10]-gingerol relative to the yield of corresponding constituent obtained by 8h Soxhlet extraction (absolute ethanol as extraction solvent).

Candida rugosa lipase (CRL) and Candida antarctica lipase A (CALA) with improved activity and selectivity were prepared for use in organic solvent media. CRL bioimprinted with fatty acids exhibited eightfold enhanced transesterification activity in hexane. Combination of bioimprinting and coating with lecithin or with immobilization did not improve the activity further. CALA was immobilized with and without bioimprinting, none of which improved the activity. All modified lipases were tested for selective ethanolysis of fish oil to concentrate omega-3 polyunsaturated fatty acids (PUFA). None of the preparations, except the immobilized ones catalysed ethanolysis. Immobilized CRL-catalyzed ethanolysis giving 27% (v/v) ethyl esters (EE) in 48 h, of which 43 mol% was oleic acid but no PUFA was detected in the EE fraction. Fatty acid selectivity of CALA was significantly improved by immobilization combined with bioimprinting, resulting in 5.5-fold lower omega-3 PUFA in EE.

Biodiesel (BD) is a fuel produced by the (trans)esterification reaction between the components of vegetable oil (or animal fat) and an alcohol. The presence of several substrates complicates analytical separation of the mixture, yet understanding of the complex reaction kinetics requires acquisition of a large body of data. The two well-established methods of gas chromatography (GC) and HPLC are time consuming and expensive when analyzing multiple samples. Additionally, it is not always possible to record all the reactants on one elution profile. We examined applicability of thin layer chromatography (TLC) for this purpose, where the detection was based on either flame ionization detector (FID) or a modified staining procedure. The suggested staining method gave no background and appeared well suited for quantitative analysis. The relevant calibrations are presented, and the general principles of analysis of nonlinear responses are discussed. Several experimental samples were produced by enzymatic conversion of rapeseed oil to BD. One reaction step resulted in 85-95% conversion (6h). The second step (after removal of glycerol and water) increased the yield to 97-98%. All components of the mixtures were separated and quantified. Relation of the BD contents measured by TLC and GC gave the values of 1.03±0.07 (TLC-staining) and 0.95±0.04 (TLC-FID), indicating applicability of the TLC-methods.

Abstract Lipase-catalyzed Knoevenagel condensation of a ketone/aldehyde (e.g., benzaldehyde 1) and the active hydrogen compound (e.g., ethyl cyanoacetate 2 or malononitrile 3) is often regarded as catalytic promiscuity. The alternative mechanism suggests partial enzymatic hydrolysis of 2, whereupon the products initiate fusion 1 + 2. Three lipases (porcine pancreatic, Mucor javanicus and Yarrowia lipolytica) did not hydrolyze 2, but significantly accelerated condensations 1 + 2 and 1 + 3 (3 is not hydrolyzable), thereby corroborating promiscuous enzymatic activity. Main conversion took place within the active site (based on competitive inhibition by caffeic acid). Yet, the “active” Ser residue of lipases was unimportant, because its covalent modification did not affect condensation. The reaction (particularly 1 + 3 condensation) was to some extent promoted by unspecific residues of lipase, as well as albumin and simple proton acceptors. Spontaneous condensation in water/ethanol surprisingly revealed kinetics with substrate saturation. We explained this depart from linearity by a two-step steady state mechanism including deprotonation of the active hydrogen substrate 3H by polar solvent, followed by direct collision of a temporary complex solvent ·H+·3– with 1. Similar mechanism with a more sophisticated binding of substrates was conjectured for the lipases.

AbstractThe property of a variety of ionic liquids (ILs) as reaction media was evaluated for the production of biodiesel by enzymatic methanolysis of rapeseed oil. The IL Ammoeng 102, containing tetraaminum cation with C18 acyl and oligoethyleneglycol units, was found to be capable of forming oil/IL biphasic reaction system by mixing with substrates, which is highly effective for the production of biodiesel with more than 98% biodiesel yield and nearly 100% conversion of oil. Conductor‐like screening model for real solvent (COSMO‐RS) in silico prediction of substrate solubility and simulation of partition coefficient change vs. reaction evolution indicated that the amphiphilic property of Ammoeng 102 might be responsible for creating efficient interaction of immiscible substrates; while big difference of partition coefficients of generated biodiesel and glycerol between the two phases suggests a large chemical potential to move reaction equilibrium for maximum oil conversion and yield of target biodiesel. The reaction behavior and specificity of oil/IL biphasic system for enzymatic production of biodiesel were theoretically delineated through COSMO‐RS computation with experimental validation. © 2010 American Institute of Chemical Engineers AIChE J, 2011