Strain engineering and fermentation technology for production of long-chain dicarboxylic acid: a review / 生物工程学报

Long-chain dicarboxylic acid (DCA), a building block for synthesizing a variety of high value-added chemicals, has been widely used in agriculture, chemical, and pharmaceutical industries. The global demand for DCA is increasing in recent years. Compared with chemical synthesis which requires harsh conditions and complicated processes, fermentative production of DCA has many unparalleled advantages, such as low cost and mild reaction conditions. In this review, we summarized the chemical and microbial synthesis methods for DCA and the commercialization status of the fermentation process. Moreover, the advances of using molecular and metabolic engineering to create high-yielding strains for efficient production of DCA were highlighted. Furthermore, the challenges remaining in the microbial fermentation process were also discussed. Finally, the perspectives for developing high titer DCA producing strains by synthetic biology were proposed.

Cloning and characterization of an oxiranedicarboxylate hydrolase from Labrys sp. WH-1 / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

OBJECTIVE@#This study aimed to clone and characterize the oxiranedicarboxylate hydrolase (ORCH) from Labrys sp. WH-1.@*METHODS@#Purification by column chromatography, characterization of enzymatic properties, gene cloning by protein terminal sequencing and polymerase chain reaction (PCR), and sequence analysis by secondary structure prediction and multiple sequence alignment were performed.@*RESULTS@#The ORCH from Labrys sp. WH-1 was purified 26-fold with a yield of 12.7%. It is a monomer with an isoelectric point (pI) of 8.57 and molecular mass of 30.2 kDa. It was stable up to 55 °C with temperature at which the activity of the enzyme decreased by 50% in 15 min (T5015) of 61 °C and the half-life at 50 °C (t1/2, 50 °C) of 51 min and was also stable from pH 4 to 10, with maximum activity at 55 °C and pH 8.5. It is a metal-independent enzyme and strongly inhibited by Cu2+, Ag+, and anionic surfactants. Its kinetic parameters (Km, kcat, and kcat/Km) were 18.7 mmol/L, 222.3 s-1, and 11.9 mmol/(L·s), respectively. The ORCH gene, which contained an open reading frame (ORF) of 825 bp encoding 274 amino acid residues, was overexpressed in Escherichia coli and the enzyme activity was 33 times higher than that of the wild strain.@*CONCLUSIONS@#The catalytic efficiency and thermal stability of the ORCH from Labrys sp. WH-1 were the best among the reported ORCHs, and it provides an alternative catalyst for preparation of L(+)-2,3-dihydrobutanedioic acid.

Melanins and lens pigments: a comparative study

Based on previous findings that lens pigments and melanins share many physicochemical properties, human lens pigments and natural (hair) and synthetic melanins were submitted to oxidation with permanganate under strong acidic conditions. This procedure has been utilized for the characterization of melanins and results in the well defined products, thiazole-4,5-dicarboxylic acid (TDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA), which can be quantitated by high performance liquid chromatography (HPLC). PTCA is regarded as a marker of black eumelanins and was therefore a main component of synthetic DOPA-eumelanin and dark hair. Its identity was established by synthesis from 5-hydroxyindole-2-carboxylic acid. TDCA derives from pheomelanins and was therefore an important component of red hair and synthetic GSH-pheomelanin. TDCA was identified by its retention time relative to PTCA. The analysis of a series of cataract digests of increasing pigmentation (type I < type IV < type V) and a purified fraction of lens pigments (DE52 pigment) revealed the presence in these preparations of both PTCA and TDCA. The concentration of TDCA significantly increased with the degree of pigmentation of the digests and reached a maximum in the DE52 pigment. The TDCA/PTCA ratio was high in the lens preparations and comparable to that given by hair pheomelanin. These findings support that pheomelanin is an integral part of lens pigments. By comparing the yields of TDCA in GSH-pheomelanin and in the purified lens pigment, a 9 per cent contribution of pheomelanin to the lens pigment was estimated