Fermentative production of cadaverine from renewable resources may support a sustainable biorefinery process to produce carbon-neutral nylons such as biopolyamide 510 (PA510). Cost-competitive production of cadaverine is a key factor in the successful commercialization of PA510. In this study, an integrated biological and chemical process involving cadaverine biosynthesis, purification, and its polymerization with sebacic acid was developed to produce bio-PA510. To stably express ldcC from Escherichia coli in an engineered Corynebacterium glutamicum PKC strain, an expired industrial L-lysine-producing strain, ldcC, was integrated into the chromosome of the C. glutamicum PKC strain by disrupting lysE and controlling its expression via a strong synthetic H30 promoter. Cadaverine was produced at a concentration of 103.78 g/L, the highest titer to date, from glucose by fed-batch culture of this engineered C. glutamgicum PKC strain. Fermentation-derived cadaverine was purified to polymer-grade biocadaverine with high purity (99%) by solvent extraction with chloroform and two-step distillation. Finally, biobased PA510 with good thermal properties (T m 215 °C and T c 158 °C) was produced by polymerization of purified cadaverine with sebacic acid. The hybrid biorefinery process combining biological and chemical processes demonstrated in this study is a useful platform for producing biobased chemicals and polymers.

L-DOPA (3,4-dihydroxyphenyl-L-alanine) has been widely used as a drug for Parkinson's disease caused by deficiency of the neurotransmitter dopamine. Since Monsanto developed the commercial process for L-DOPA synthesis for the first time, most of currently supplied L-DOPA has been produced by the asymmetric method, especially asymmetric hydrogenation. However, the asymmetric synthesis shows critical limitations such as a poor conversion rate and a low enantioselectivity. Accordingly, alternative biotechnological approaches have been researched for overcoming the shortcomings: microbial fermentation using microorganisms with tyrosinase, tyrosine phenol-lyase, or p-hydroxyphenylacetate 3-hydroxylase activity and enzymatic conversion by immobilized tyrosinase. Actually, Ajinomoto Co. Ltd commercialized Erwinia herbicola fermentation to produce L-DOPA from catechol. In addition, the electroenzymatic conversion system was recently introduced as a newly emerging scheme. In this review, we aim to not only overview the biotechnological L-DOPA production methods, but also to briefly compare and analyze their advantages and drawbacks. Furthermore, we suggest the future potential of biotechnological L-DOPA production as an industrial process.

Whole-cell conversion of cyclohexanone to epsilon-caprolactone was attempted by recombinant Escherichia coli BL21(DE3) expressing cyclohexanone monooxygenase (CHMO) of Acinetobacter calcoaceticus NCIMB 9871. High concentrations of cyclohexanone and epsilon-caprolactone reduced CHMO-mediated bioconversion of cyclohexanone to epsilon-caprolactone in the resting recombinant E. coli cells. Metabolically active cells were employed by adopting a fed-batch culture to improve the production of epsilon-caprolactone from cyclohexanone. A glucose-limited fed-batch Baeyer-Villiger oxidation where a cyclohexanone level was maintained less than 6 g/l resulted in a maximum epsilon-caprolactone concentration of 11.0 g/l. The maximum epsilon-caprolactone concentration was improved further to 15.3 g/l by coexpression of glucose-6-phosphate dehydrogenase, an NADPH-generating enzyme encoded by the zwf gene which corresponded to a 39% enhancement in epsilon-caprolactone concentration compared with the control experiment performed under the same conditions.

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Corynebacterium glutamicum is an important microorganism in the biochemical industry for the production of various platform chemicals. However, despite its importance, a limited number of studies have been conducted on how to constitute gene expression cassettes in engineered C. glutamicum to obtain desired amounts of the target products. Therefore, in this study, six expression cassettes for the expression of the second lysine decarboxylase of Escherichia coli, LdcC, were constructed using six synthetic promoters with different strengths and were examined in C. glutamicum for the production of cadaverine. Among six expression cassettes, the expression of the E. coli ldcC gene under the PH30 promoter supported the highest production of cadaverine in flask and fed-batch cultivations. A fed-batch fermentation of recombinant C. glutamicum expressing E. coli ldcC gene under the PH30 promoter resulted in the production of 40.91 g/L of cadaverine in 64 h. This report is expected to contribute toward developing engineered C. glutamicum strains to have desired features.

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Coenzyme Q(10) (CoQ(10)) is a quinine consisting of ten units of the isoprenoid side-chain. Because it limits the oxidative attack of free radicals to DNA and lipids, CoQ(10) has been used as an antioxidant for foods, cosmetics and pharmaceuticals. Decaprenyl diphosphate synthase (DPS) is the key enzyme for synthesis of the decaprenyl tail in CoQ(10) with isopentenyl diphosphate. The ddsA gene coding for DPS from Gluconobacter suboxydans was expressed under the control of an Escherichia coli constitutive promoter. Analysis of the cell extract in recombinant E. coli BL21/pACDdsA by high performance liquid chromatography and mass spectrometry showed that CoQ(10) rather than endogenous CoQ(8) was biologically synthesized as the major coenzyme Q. Expression of the ddsA gene with low copy number led to the accumulation of CoQ(10) to 0.97 mg l(-1) in batch fermentation. A high cell density (103 g l(-1)) in fed-batch fermentation of E. coli BL21/pACDdsA increased the CoQ(10) concentration to 25.5 mg l (-1) and its productivity to 0.67 mg l(-1) h(-1), which were 26.0 and 6.9 times higher than the corresponding values for batch fermentation.