Enantioselective, continuous (R)- and (S)-2-butanol synthesis: Achieving high space-time yields with recombinant E. coli cells in a micro-aqueous, solvent-free reaction system

Recent advances in whole cell biocatalysis techniques bridging from investigative to industrial scale

“…The concept of neat substrate systems was further adapted to the stereoselective production of (R)-and (S)-2-butanol 'Smart' diol cosubstrates are oxidized twice thus generating two equivalents of regenerated cofactor before lactone formation [17]. [29 ]. This synthesis is particularly challenging, as the reversibility of the reaction leads to racemization of the product, which decreases the optical purity.…”

“…This reactor was constantly flushed with a mixture of 2-butanon, 2-propanol (as cosubstrate for cofactor regeneration) and 10% triethanolamine buffer. The reactions in this almost neat, monophasic substrate system could be optimized for maximum productivity yielding 2278 g L À1 d À1 (R)-2-butanol with a stereoselectivity of 96.6% and 180-461 g L À1 d À1 (S)-2-butanol (ee 98%), respectively [29 ].…”

Modularized Biocatalysis: Immobilization of Whole Cells for Preparative Applications in Microaqueous Organic Solvents

“…[18] On the other hand, the application of al yophilized whole-cell catalyst has the advantages of (i)non eed for expensive enzyme purification, (ii)facilitated handling (compared to wet cells), (iii)excellent storability, (iv) an often increased catalyst stability (compared to free enzyme), and (v) no need to add any cofactor externally. [18,[23][24][25] In combination with microaqueous solvents, high concentrations of poorly water-soluble compounds can be applieda s The use of whole-cell biocatalystse nables catalyst application in microaqueous reactions ystems, in which the liquid phase consists of high substrate loadings in organics olvents, to enable access to high concentrations of easy-to-purify product. One current research focus is the modularization of single reaction steps to (i)enable flexible combinations into multi-step enzyme reactions, (ii)investigate ideal reactionc onditions, and (iii)facilitate catalyst handlinga nd recycling.…”

Activity of Lactobacillus brevis Alcohol Dehydrogenase on Primary and Secondary Alcohol Biofuel Precursors

“…[7]. Several studies, meanwhile, have studied the ability of LbADH to catalyze the stereoselective reduction of 2-butanone [8][9][10]. Erdmann et al, for example, recently demonstrated that whole cells of recombinant Escherichia coli expressing LbADH could be employed in a novel continuous reactor process to convert 2-butanone to (R)-2-butanol at >99% conversion and >96% e.e., while also achieving space time yields of ~2300 g/L-d [8].…”

“…In addition to their roles as building-block chemicals [8], short chain aliphatic alcohols are of particular interest as the potential gasoline alternatives. Among aliphatic alcohols, those with >2 carbons continue to emerge as attractive second-generation biofuel targets [11].…”