L-phenylacetylcarbinol production by yeast petite mutants

Microbial synthesis of branched-chain β,γ-diols from amino acid metabolism

Microbial synthesis of chemicals using renewable feedstocks has gained interest due to its sustainability. The class of β,γ-diols has unique chemical and physical properties, making them valuable for diverse applications. Here, we report a biosynthetic platform in Escherichia coli for the synthesis of branched-chain β,γ-diols from renewable feedstocks. Firstly, we identify an acetohydroxyacid synthase from Saccharomyces cerevisiae to catalyze the condensation of branched-chain aldehydes with pyruvate, forming α-hydroxyketones. Next, de novo production of branched-chain β,γ-diols (4-methylpentane-2,3-diol, 5-methylhexane-2,3-diol and 4-methylhexane-2,3-diol) is realized from branched-chain amino acids (BCAA) metabolism. After systematic optimization of the BCAA pathway, we have achieved high-specificity production of 4-methylpentane-2,3-diol from glucose, achieving 129.8 mM (15.3 g/L) 4-methylpentane-2,3-diol with 72% of the theoretical yield. In summary, our work demonstrates the synthesis of structurally diverse branched-chain β,γ-diols, highlighting its potential as a versatile carbon elongation system for other β,γ-diol productions.

Utilization of agricultural wastes for co-production of xylitol, ethanol, and phenylacetylcarbinol: A review

Corn, rice, wheat, and sugar are major sources of food calories consumption thus the massive agricultural waste (AW) is generated through agricultural and agro-industrial processing of these raw materials. Biological conversion is one of the most sustainable AW management technologies. The abundant supply and special structural composition of cellulose, hemicellulose, and lignin could provide great potential for waste biological conversion. Conversion of hemicellulose to xylitol, cellulose to ethanol, and utilization of remnant whole cells biomass to synthesize phenylacetylcarbinol (PAC) are strategies that are both eco-friendly and economically feasible. This co-production strategy includes essential steps: saccharification, detoxification, cultivation, and biotransformation. In this review, the implemented technologies on each unit step are described, the effectiveness, economic feasibility, technical procedures, and environmental impact are summarized, compared, and evaluated from an industrial scale viewpoint.

Process optimization for biosynthesis of pyruvate decarboxylase (PDC) and Neuberg’s ketol (PAC) from a novel Pichia cecembensis through response surface methodology

Purpose

Phenylacetylcarbinol (PAC) is an intermediate for the synthesis of several active pharmaceutical ingredients (ephedrine, pseudoephedrine, norephedrine, etc.) used for the production of antiasthematics and decongestants. An efficient biosynthesis of PAC through condensation of benzaldehyde and acetaldehyde catalyzed by a solvent tolerant pyruvate decarboxylase (PDC) is being reported. A process for the biosynthesis of PAC was designed and optimized through response surface methodology (RSM) in the present study.

Methods

The effects of incubation time (8–18 h), incubation temperature (30–38 °C), medium pH (4–10), and inoculum size (4–10%) on PAC yield, sugar consumption, and PDC activity were determined through submerged fermentation using a newly isolated potent yeast strain of Pichia cecembensis. PAC was quantified spectrophotometerically and through HPLC. PDC produced was exposed to 40 mM benzaldehyde as whole cells, crude extract, and partialy purified preparation to check its stability against the said solvent.

Results

The highest PDC activity and PAC yield during present study were found to be 56.27 U/ml and 8.44 g/l, respectively. The yield of PAC was increased by 71% (2.22 to 8.44 g/l) after process optimization through RSM with incubation time of 13 h, incubation temperature of 33 °C, and 18% total sugar as significant factors (P-values, 0.902, 0.260, and 0.247, respectively). R-squared value of 0.770 and Adeq Precision value of 4.888 show the goodness of fit of the process design. PDC is used in the form of Pichia cecembensis whole cells revealed higher stability towards benzaldehyde and elevated temperature as compared to partially purified PDC. Whole cells and partially purified PDC showed half-lives of 240 and 72 h at 4 °C, whereas 33 and 28.5 h at 25 °C. PAC was purified though HPLC with a purity level of 76.18%.

Conclusion

Incubation time, temperature, and sugar concentration were found to be significant factors for the biosynthesis of PAC. A newly isolated Pichia cecembensis produced a highly active, solvent, and temperature-tolerant pyruvate decarboxylase (PDC) which is superior to its counterpart being presently used in the industry. Hence, this novel yeast species is a promising candidate for commercial production of PAC and other related APIs owing to its highly stable PDC.

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Biotransformation of benzaldehyde into L-phenylacetylcarbinol using magnetic nanoparticles-coated yeast cells

OBJECTIVES

The yeast cells were coated with Fe₃O₄ magnetic nanoparticles and employed as biocatalyst for the microbial biotransformation of benzaldehyde into L-phenylacetylcarbinol (L-PAC).

RESULTS

Saccharomyces cerevisiae CEN.PK113-7D yeast cells were coated with magnetic nanoparticles to facilitate the cells separation process. Transmission electron microscopy, powder XRD diffraction, and vibrating sample magnetometer were used to characterize magnetic nanoparticles and magnetic nanoparticle-coated yeast cells. Then the reusability of magnetically recoverable cells in production of L-PAC was investigated. Results show that coating yeast cells with magnetic nanoparticles does not affect their size and structure. Coated cells were also used in seven consecutive batch cycles and no significant reduction for L-PAC titer was observed in any of the cycles.

CONCLUSION

Coating yeast cells with magnetic nanoparticles enabled rapid separation and reuse of cells in several successive batch cycle without affecting their ability to produce L-PAC.