Stereo-selective conversion of mandelonitrile to R-−-mandelic acid using immobilized cells of recombinant Escherichia coliReport as inadecuate




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3 Biotech

, Volume 2, Issue 4, pp 319–326

First Online: 29 March 2012Received: 22 January 2012Accepted: 14 March 2012

Abstract

Immobilized cells of a recombinant Escherichia coli expressing nitrilase from Pseudomonas putida were used to catalyze the hydrolysis of mandelonitrile 2-hydroxy-2-phenylacetonitrile to R-−-mandelic acid. The cells had been immobilized by entrapment in an alginate matrix. Conditions for the hydrolysis reaction were optimized in shake flasks and in a packed bed reactor. In shake flasks the best conditions for the reaction were a temperature of 40 °C, pH 8, biocatalyst bead diameter of 4.3 mm, sodium alginate concentration in the gel matrix of 2 % w-v, g-100 mL, a cell dry mass concentration in the bead matrix of 20 mg-mL, an initial substrate concentration of 50 mM and a reaction time of 60 min. Under these conditions, the conversion of mandelonitrile was nearly 95 %. In the packed bed reactor, a feed flow rate of 20 mL-h at a substrate concentration of 200 mM proved to be the best at 40 °C, pH 8, using 4.3 mm beads 2 % w-v sodium alginate in the gel matrix, 20 mg dry cell concentration per mL of gel matrix. This feed flow rate corresponded to a residence time of 0.975 h in the packed bed.

KeywordsNitrilase Mandelic acid Mandelonitrile Packed bed reactor Immobilized cells  Download fulltext PDF



Author: Sandip V. Pawar - Vachan Singh Meena - Shubhangi Kaushik - Ashwini Kamble - Sandeep Kumar - Yusuf Chisti - U. C. Banerje

Source: https://link.springer.com/



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