Whole-cell biocatalysts by design

Abstract

Whole-cell biocatalysts provide unique advantages and have been widely used for the efficient biosynthesis of value-added fine and bulk chemicals, as well as pharmaceutically active ingredients. What is more, advances in synthetic biology and metabolic engineering, together with the rapid development of molecular genetic tools, have brought about a renaissance of whole-cell biocatalysis. These rapid advancements mean that whole-cell biocatalysts can increasingly be rationally designed. Genes of heterologous enzymes or synthetic pathways are increasingly being introduced into microbial hosts, and depending on the complexity of the synthetic pathway or the target products, they can enable the production of value-added chemicals from cheap feedstock. Metabolic engineering and synthetic biology efforts aimed at optimizing the existing microbial cell factories concentrate on improving heterologous pathway flux, precursor supply, and cofactor balance, as well as other aspects of cellular metabolism, to enhance the efficiency of biocatalysts. In the present review, we take a critical look at recent developments in whole-cell biocatalysis, with an emphasis on strategies applied to designing and optimizing the organisms that are increasingly modified for efficient production of chemicals.

A Generalized Kinetic Framework Applied to Whole‐Cell Bioelectrocatalysis in Bioflow Reactors Clarifies Performance Enhancements for Geobacter Sulfurreducens Biofilms

“…Control over substrate concentration and reactor feeding strategy are the most important factors for optimization of whole‐cell biocatalysis ,. Chemostat bioreactors can impose tunable concentrations against the biofilm and eliminate nutrient depletion and product accumulation which occurs between solution replenishment cycles in bulk reactors . However, latency in manipulations of reaction conditions during reaction optimization and fundamental research is a drawback.…”

“…As applied to the study of G. sulfurreducens biofilms, a flow‐adapted version of the Michaelis‐Menten equation was used for the first time to understand and develop whole‐cell catalysis while leveraging the advantages of microfluidic biofilm flow reactors. Various applications can be envisioned, especially those related to synthetic biology and metabolic engineering in which cells are effectively considered as units of production for valuable products of bulk and fine chemicals . In addition, characterization of enzymes within their native (cellular) environment is an important goal in the field of enzymology .…”

The Kinetic Resolution of Racemic Amines Using a Whole-Cell Biocatalyst Co-Expressing Amine Dehydrogenase and NADH Oxidase

“…Therefore, recombinant Escherichia coli cells co-expressing AmDH and Nox were used as biocatalysts (vide infra). The use of whole-cells instead of isolated enzymes in biological processes has a simple and economical advantage, as the cost for cell lysis and purification is reduced [30]. Another advantage of a whole-cell reaction system is that cofactor-dependent enzymatic reactions can be effectively performed by using endogenous cofactors without adding costly cofactors [30].…”

“…The use of whole-cells instead of isolated enzymes in biological processes has a simple and economical advantage, as the cost for cell lysis and purification is reduced [30]. Another advantage of a whole-cell reaction system is that cofactor-dependent enzymatic reactions can be effectively performed by using endogenous cofactors without adding costly cofactors [30]. Sometimes, a whole cell reaction is less susceptible to enzyme inhibition by substrate and product due to the diffusion barrier of the cell membrane [31].…”

Whole‐cell biocatalysis platform for gram‐scale oxidative dearomatization of phenols

“…Recently, significant effort has been dedicated to establishing efficient biocatalytic reaction platforms for a wide variety of transformations. A number of approaches have been developed for conducting preparative‐scale biocatalytic reactions, including reactions with purified enzymes, crude cell lysates (Rudroff et al., ; Sheldon & Woodley, ) immobilized enzymes (Liang, Li, & Yang, ; Sheldon & van Pelt, ; Soares et al., ) lyophilized lysates, and wet whole cells (de Carvalho, ; Lin & Tao, ; Wachtmeister, Mennicken, Hunold, & Rother, ). Enzymes in various forms can be employed in batch or flow reactors (Britton, Majumdar, & Weiss, ; Tamborini, Fernandes, Paradisi, & Molinari, ).…”