Due to the increasing need for greener and sustainable alternatives to fossil-based industrial chemicals and products, development of efficient synthesis of biomass-based platform chemicals is an attractive goal. 5-Hydroxymethylfurfural (HMF) derived 2,5-bis(hydroxymethyl)furan (BHMF) is one of the most targeted green chemicals, since it is a valuable building block for production of various useful compounds. Herein we described the efficient enzyme catalyzed double esterification of BHMF with saturated long-chain fatty acids using biomass-derived 2-methyl-tetrahydrofuran (2-MTHF) as solvent, providing an efficient synthetic route with >99% overall conversion (BHMF mono-and diesters) and between 89 and 99% conversion into the targeted BHMF diesters. The optimized large-scale procedure yielded easily isolable and chemically pure products useful to improve the cetane number of biodiesel.

Fatty acid diesters of 2,5-bis-(hydroxymethyl)­furan (BHMF), promising candidates as sustainable bioadditives for increasing the cetane number of biodiesel fuels, were prepared through a solvent-free Novozym 435-mediated diesterification of BHMF with a fatty acid mixture (FAM) resulting from the hydrolysis of commercial sunflower oil. Under solvent-free conditions and a 15 mbar vacuum, high conversions into diesters were obtained in the heterogeneous reaction, after the gradual solubilization of BHMF. After optimization studies (temperature, reaction time, BHMF–FAM ratio, and biocatalyst loading), more than 97% conversion into diesters was achieved. The calculated sustainability metrics support the fact that the currently described solvent-free method represents an improved synthetic procedure for the preparation of BHMF fatty acid diesters.

In this study, yeast strains were screened and immobilized in a form preserving the multifaceted biocatalytic activity. Immobilization of the silica-supported whole cells of various yeasts, such as Lodderomyces elongisporus, Pichia carsonii, Candida norvegica, and Debaryomyces fabryi, by sol−gel entrapment resulted in easy-to-handle biocatalysts that mediated efficiently different types of synthetic reactions. In the present study, the enantiotope selective reduction of prochiral ketones 1a−d and the acyloin condensation of benzaldehyde 3 were studied, representing two remarkably diverse types of biotransformation. The yeast cell biocatalystsin the presence of fresh or recovered NADH cofactorcould be applied for continuous-flow bioreduction of ketones 1a−d with moderate to good yields (20 to 92%) and excellent enantiomeric purity (>99%). Immobilized L. elongisporus and P. carsonii cells could also mediate acyloin condensation of benzaldehyde 3 in batch as well as in continuousflow mode. The switchable biocatalytic activity of the immobilized yeast cells was demonstrated by consecutive biotransformations under continuous-flow conditions involving reduction of phenylacetone 1a to (S)-phenylpropane-2-ol [(S)-2a] first, followed by conversion of benzaldehyde 3 to (R)-1-hydroxy-1-phenylpropan-2-one [(R)-4] and reduction of 1a to (S)-2a again by using the same packed-bed bioreactor.

In this study, an efficient and generally applicable 2 nd generation sol -gel entrapment method was developed for immobilization of yeast cells. Cells of Lodderomyces elongisporus, Candida norvegica, Debaryomyces fabryi, Pichia carsonii strains in admixture with hollow silica microspheres support were immobilized in sol -gel matrix obtained from polycondensation of tetraethoxysilane. As biocatalysts in the selective acyloin condensation of benzaldehyde catalyzed by pyruvate decarboxylase of the yeast, the novel immobilized whole-cell preparations were compared to other states of the cells such as freshly harvested wet cell paste, lyophilized cells and sol -gel entrapped preparations without hollow silica microspheres support. Reusability and storability studies designated this novel 2 nd generation solgel method as a promising alternative for solid formulation of whole-cells bypassing expensive and difficult downstream steps while providing easy-to-handle and stable biocatalysts with long-term preservation of the biocatalytic activity.

We report a simple enzymatic procedure for the synthesis of short-chained flavor esters by direct esterification of natural acids with short-chain primary alcohols mediated by lipase B from Candida antarctica entrapped in a tailored sol–gel matrix in the presence of three additives, using vacuum for water removal. Maximal immobilization yields (100%) were obtained for all three biocatalysts, while the enzyme loading and the synthetic activity depend on the used additive (6.7, 7.6, and 7.7 μg enzyme/mg biocatalyst for β-cyclodextrin, polyvinyl alcohol, and glycerol, respectively, and 76–110% recovered activity as compared with free lipase). The process was optimized using the reaction of hexan-1-ol with butyric acid as the model with significant conversion improvements (from <40% to >94%) reducing the alcohol/enzyme ratio (from 100:1 to 25:1 weight ratio) for all novel biocatalysts. Other short-chain flavor esters were prepared with excellent yields (>90%) under the previously established optimal conditions. Atom economy (90.53), E-factor (17.22), atom efficiency (88.36), mass intensity (18.58), and reaction mass efficiency (60.07) as relevant sustainability metrics were calculated for the preparative scale model reaction with glycerol as the additive. Based on our results, this green and sustainable new approach can be used for the synthesis of many flavor esters.