High-level expression of nitrile hydratase from Pantoea sp. At-9b in Escherichia coli

Tuning an efficient Escherichia coli whole-cell catalyst expressing l-pantolactone dehydrogenase for the biosynthesis of d-(-)-pantolactone

d-(-)-Pantolactone (DPL) is a key intermediate for the production of d-(+)-pantothenate (vitamin B5). Deracemization of d,l-pantolactone (D,L-PL) through oxidizing l-(+)-pantolactone (LPL) to ketopantoyl lactone (KPL) and subsequently reducing KPL to DPL is a promising route for synthesizing DPL. Herein, a newly mined l-pantolactone dehydrogenase from Rhodococcus hoagie (RhoLPLDH) was used for the oxidative dehydrogenation of LPL. To alleviate inclusion bodies formed by membrane-bound RhoLPLDH intracellular expression in E. coli, strategies involving chaperone assistance and decreasing induction temperature were used to achieve RhoLPLDH soluble expression. To enhance its activity, directed evolution and hydrophilicity-based engineering yielded increased catalytic activity and thermostability. 1M LPL was efficiently converted to KPL by engineering strain CM5 co-expressing RhoLPLDH^{L254I/V241I/I156L/F224Q/N164K} and chaperone. A "two stages in one-pot" method was employed in deracemization of 1M D,L-PL with 91.2% yield. These results demonstrated that CM5 catalyst exhibits great potential in enzyme cascade deracemization for the production of DPL.

Nitrile Hydratases: From Industrial Application to Acetamiprid and Thiacloprid Degradation

The widespread application of neonicotinoid insecticides (NEOs) in agriculture causes a series of environmental and ecological problems. Microbial remediation is a popular approach to relieve these negative impacts, but the associated molecular mechanisms are rarely explored. Nitrile hydratase (NHase), an enzyme commonly used in industry for amide production, was discovered to be responsible for the degradation of acetamiprid (ACE) and thiacloprid (THI) by microbes. Since then, research into NHases in NEO degradation has attracted increasing attention. In this review, microbial degradation of ACE and THI is briefly described. We then focus on NHase evolution, gene composition, maturation mechanisms, expression, and biochemical properties with regard to application of NHases in NEO degradation for bioremediation.