Production of (Z)-11-(heptanoyloxy)undec-9-enoic acid from ricinoleic acid by utilizing crude glycerol as sole carbon source in engineered Escherichia coli expressing BVMO-ADH-FadL

Directed evolution of Baeyer-Villiger monooxygenase for highly secretory expressed in Pichia pastoris and efficient preparation of chiral pyrazole sulfoxide

The methylotrophic yeast Pichia pastoris (Komagataella phaffii) is a highly distinguished expression platform for the excellent synthesis of various heterologous proteins in recent years. With the advantages of high-density fermentation, P. pastoris can produce gram amounts of recombinant proteins. While not every protein of interest can be expressed to such high titers, such as Baeyer-Villiger monooxygenase (BVMO) (AcPSMO) which is responsible for pyrazole sulfide asymmetric oxidation. In this work, an excellent yeast expression system was established to facilitate efficient AcPSMO expression, which exhibited 9.5-fold enhanced secretion. Subsequently, an ultrahigh throughput screening method based on fluorescence-activated cell sorting by fusing super folder green fluorescent protein (sfGFP) in the C-terminal of AcPSMO was developed, and directed evolution was performed. The protein expression level of the superior mutant AcPSMOP1 (S58T/T252P/E336N/H456D) reached 84.6 mg/L at 100 mL shaking flask, which was 4.7 times higher than the levels obtained with the wild-type. Finally, the optimized chassis cells were used for high-density fermentation on a 5-L scale, and AcPSMOP1 protein yield of 3.4 g/L was achieved, representing approximately 85% of the total protein secreted. By directly employing the pH-adjusted supernatant as a biocatalyst, 20 g/L pyrmetazole sulfide was completely transformed into the corresponding (S)-sulfoxide, with a 78.8% isolated yield. This work confers dramatic benefits for efficient secretion of other BVMOs in P. pastoris.

Enzymatic utilization of oil and lignocellulosic biomass using halophilic marine bacteria Micrococcus luteus and Pseudoalteromonas peptidolytica

In this study, hydrolytic and oxidative activities of enzymes isolated from halophilic microbes were characterized and applied for biomass utilization. First, lipase from Micrococcus luteus, and peroxidase and laccase from Pseudoalteromonas phenolica and Pseudoalteromonas peptidolytica were selected and their catalytic activities were determined, respectively. The M. luteus lipase encoding gene was synthesized after codon-optimization and could be successfully expressed in Escherichia coli with the assist of the Tif chaperone protein. The purified enzyme showed 119.13 ± 7.18 and 34.42 ± 5.91 U/mL of lipase and esterase activities, respectively. Moreover, the M. luteus lipase was applied for hydrolysis of the triglycerides mixture, which resulted in 182.9 ± 11.1 mg/L/h of glycerol productivity. Next, peroxidase and laccase activities of P. phenolica and P. peptidolytica were determined, and extracellular enzymes of P. peptidolytica was applied for lignocellulosic biomass degradation, which resulted in 91.9 μg glucose/mg lignocellulose of production yields. Finally, the hydrolytic and oxidative activities of the enzymes from halophilic microbes could be further utilized for biomass treatment and biochemical production.

Whole-cell biocatalysis using cytochrome P450 monooxygenases for biotransformation of sustainable bioresources (fatty acids, fatty alkanes, and aromatic amino acids)

Cytochrome P450s (CYPs) are heme-thiolated enzymes that catalyze the oxidation of CH bonds in a regio and stereoselective manner. Activation of the non-activated carbon atom can be further enhanced by multistep chemo-enzymatic reactions; moreover, several useful chemicals can be synthesized to provide alternative organic synthesis routes. Given their versatile functionality, CYPs show promise in a number of biotechnological fields. Recently, various CYPs, along with their sequences and functionalities, have been identified owing to rapid developments in sequencing technology and molecular biotechnology. In addition to these discoveries, attempts have been made to utilize CYPs to industrially produce biochemicals from available and sustainable bioresources such as oil, amino acids, carbohydrates, and lignin. Here, these accomplishments, particularly those involving the use of CYP enzymes as whole-cell biocatalysts for bioresource biotransformation, will be reviewed. Further, recently developed biotransformation pathways that result in gram-scale yields of fatty acids and fatty alkanes as well as aromatic amino acids, which depend on the hosts used for CYP expression, and the nature of the multistep reactions will be discussed. These pathways are similar regardless of whether the hosts are CYP-producing or non-CYP-producing; the limitations of these methods and the ways to overcome them are reviewed here.