Enzymatic aromatization of 4-ketocyclohexanecarboxylic acid to p-hydroxybenzoic acid

$\text{Corynebacterium cyclohexanicum}$ grows well on cyclohexane carboxylic acid as the sole carbon source, and accumulates a large amount of 4-ketocyclohexanecarboxylic acid in the culture medium at an early growth phase. When this keto acid was aerobically incubated with a crude extract of the organism, an acidic product was produced. Under anaerobic conditions, the same product was obtained using K₃Fe(CN)₆ as electron acceptor. The product was identified as p-hydroxybenzoic acid by means of gas-liquid chromatography, infrared spectroscopy, and mass spectroscopy. Two pathways are proposed for the aromatization of 4-ketocyclohexanecarboxylic acid.     

Bioconversion of linoleic acid to conjugated linoleic acid byBifidobacterium breve

The bioconversion of linoleic acid (LA) to conjugated linoleic acid (CLA) was investigated to examine LA-adaptation ofBifidobacterium breve KCTC 3461 to additions of 1 to 5 mg/mL of LA overtime. To induce LA-adaptation,B. breve KCTC 3461 was treated with LA, according to three schemes. For LA-adaptedB. breve the maximum concentration of CLA, 300–350 μg/mL, was obtained in cys-MRS medium containing 1 mg/mL of LA. The CLA production significantly increased with increasing LA concentration, from 1 to 4 mg/mL, but the conversion of LA to CLA gradually decreased. The CLA production capability ofB. breve, and its tolerance, improved significantly with LA-adaptation. The addition of LA (1 mg/mL) into the culture broth after 24 h of cultivation in a 100-mL media bottle was most effective at promoting CLA production. In a 2.5-L stirred-tank bioreactor, the observed conversion and productivity of 56.6% and 35.4 μgml⁻¹h⁻¹, respectively, by LA-adaptedB. breve were approximately 6.6 and 9.8 times higher than those of LA-unadaptedB. breve.     

Aerobic biotransformation of 4-fluorocinnamic acid to 4-fluorobenzoic acid

The biotransformation of 4-fluorocinnamic acid (FCA) using non-acclimated industrial activated sludge was investigated. FCA is a common intermediate in organic synthesis, and it is often present in aqueous waste streams. Hence, the biotransformation reactions this compound undergoes when exposed to activated sludge micro-organisms should be understood before waste streams are sent to biological wastewater treatment plants (WWTPs). FCA biotransformation was monitored using a wide range of analytical techniques. These techniques were used to monitor not only FCA disappearance, but also the formation of degradation products, in order to propose the metabolic pathway. FCA was biotransformed to 4-fluorobenzoic acid via the formation of 4-fluoroacetophenone. The removal of FCA up to 200 mg L^-1 followed first order kinetics. The half-lives for removal of FCA from the test solutions supplied with 200 mg L^-1, 100 mg L^-1, and 50 mg L^-1 were 53, 18, and 5 hours respectively.