Expression of the Fusarium oxysporum lactonase gene in Aspergillus oryzae: molecular properties of the recombinant enzyme and its application

Biocatalysis of heterogenously-expressed d-lactonohydrolases and its efficient preparation of desirable d-pantoic acid

d-Pantoic acid (D-PA) is an essential intermediate for the production of d-pantolactone. Here, three d-lactonohydrolases (D-Lacs), namely, Fm-Lac from Fusarium moniliforme SW-902, Fp-Lac from Fusarium proliferatum Nirenberg ECU2002, and Fo-Lac from Fusarium oxysporum AKU3702 were heterogeneously expressed in Pichia pastoris. The constructed recombinant strains produced D-Lacs of 1263 U/mL, 1025 U/mL, and 948 U/mL in a 3-L fermenter, respectively. Simultaneously, these three D-Lacs were used to resolve racemic pantolactone (DL-PL), the hydrolysis rate by Fo-Lac over 40% and the enantiomeric excesses was 99% after 4 h reaction, which outperformed Fm-Lac and Fp-Lac. Under the 800 mL scale reaction, the hydrolysis rate of DL-PL reached 39.2% with a D-PA concentration of 144.6 g/L and space-time yield of 36.2 g/L/h correspondingly. This is the highest catalytic efficiency reported so far, which shows that D-Lac heterologously expressed by P. pastoris has excellent industrial application prospects.

Industrial kinetic resolution of d,l-pantolactone by an immobilized whole-cell biocatalyst

Immobilized whole-cells of Pichia pastoris harboring recombinant d-lactonase were entrapped in calcium alginate gels and used as an efficient biocatalyst for catalytic kinetic resolution of d,l-pantolactone. The immobilized whole-cell biocatalyst exhibited good catalytic stability, which was applied for stereospecific hydrolysis of d-pantolactone for up to 56 repeated batch reactions without obvious loss in the catalytic activity and enantioselectivity.

Immobilized whole-cells of Pichia pastoris harboring recombinant d-lactonase were entrapped in calcium alginate gels and used as an efficient biocatalyst for catalytic kinetic resolution of d,l-pantolactone.

Biocatalytic kinetic resolution of d,l-pantolactone by using a novel recombinant d-lactonase

d-Pantolactone is a key chiral intermediate for the synthesis of d-pantothenic acid and its derivatives. Biocatalytic kinetic resolution of d,l-pantoyl lactone using d-lactonase is an efficient route to synthesize d-pantolactone. In this study, we report the expression of a novel d-lactonase TSDL in Escherichia coli host. The recombinant TSDL exhibited high hydrolysis activity and enantioselectivity toward d-pantolactone. The reaction conditions of the recombinant TSDL-catalyzed kinetic resolution of d,l-pantolactone was systematically investigated by whole cell biocatalysis. In addition, a preparative-scale reaction for bioproduction of d-pantoic acid was examined under optimized reaction conditions. This study presented an alternative enzymatic process for kinetic resolution of d,l-pantolactone.

d-Pantolactone is a key chiral intermediate for the synthesis of d-pantothenic acid and its derivatives.

A novel method of producing the pharmaceutical intermediate (R)-2-chloromandelic acid by bioconversion

(R)-2-Chloromandelic acid (R-CM) is one of the chiral building blocks used in the pharmaceutical industry. As a result of screening for microorganisms that asymmetrically hydrolyze racemic 2-chloromandelic acid methyl ester (CMM), Exophiala dermatitidis NBRC6857 was found to produce R-CM at optical purity of 97% ee. The esterase that produces R-CM, EstE, was purified from E. dermatitidis NBRC6857, and the optimal temperature and pH of EstE were 30°C and 7.0, respectively. The estE gene that encodes EstE was isolated and overexpressed in Escherichia coli JM109. The activity of recombinant E. coli JM109 cells overexpressing estE was 553 times higher than that of E. dermatitidis NBRC6857. R-CM was produced at conversion rate of 49% and at optical purity of 97% ee from 10% CMM with 0.45 mg-dry-cell/L recombinant E. coli JM109 cells. Based on these findings, R-CM production by bioconversion of CMM may be of interest for future industrial applications.

Microbial enzymes involved in lactone compound metabolism and their biotechnological applications

Lactone compounds are widely distributed in nature and play important roles in organisms. These compounds are synthesized and metabolized enzymatically in vivo; however, detailed investigation of these enzymes lags behind that of other common enzymes. In this paper, recent work on the enzymes involved in the metabolism of lactone compounds will be reviewed. In particular, fundamental and application studies on lactonases and Baeyer-Villiger monooxgenases of microbial origin are described.

Computational analysis of the Phanerochaete chrysosporium v2.0 genome database and mass spectrometry identification of peptides in ligninolytic cultures reveal complex mixtures of secreted proteins

The white-rot basidiomycete Phanerochaete chrysosporium employs extracellular enzymes to completely degrade the major polymers of wood: cellulose, hemicellulose, and lignin. Analysis of a total of 10,048 v2.1 gene models predicts 769 secreted proteins, a substantial increase over the 268 models identified in the earlier database (v1.0). Within the v2.1 'computational secretome,' 43% showed no significant similarity to known proteins, but were structurally related to other hypothetical protein sequences. In contrast, 53% showed significant similarity to known protein sequences including 87 models assigned to 33 glycoside hydrolase families and 52 sequences distributed among 13 peptidase families. When grown under standard ligninolytic conditions, peptides corresponding to 11 peptidase genes were identified in culture filtrates by mass spectrometry (LS-MS/MS). Five peptidases were members of a large family of aspartyl proteases, many of which were localized to gene clusters. Consistent with a role in dephosphorylation of lignin peroxidase, a mannose-6-phosphatase (M6Pase) was also identified in carbon-starved cultures. Beyond proteases and M6Pase, 28 specific gene products were identified including several representatives of gene families. These included 4 lignin peroxidases, 3 lipases, 2 carboxylesterases, and 8 glycosyl hydrolases. The results underscore the rich genetic diversity and complexity of P. chrysosporium's extracellular enzyme systems.

Whole organism biocatalysis

The use of biocatalysts for the industrial synthesis of chemicals has been attracting much attention as an environment-friendly synthetic method. Microbial cells play a leading role in 'chemo-enzymatic synthesis' because of their great diversity. Several microbes with unique catalytic abilities have been found through intensive screening and put to practical use. Besides, advanced molecular biological techniques are powerful tools for developing more satisfactory biocatalysts.