A microbial biosensor for trimethylamine using Pseudomonas aminovorans cells.

A biosensor system based on the difference in the oxygen uptake response of two microbial electrodes was developed to monitor trimethylamine (TMA). The first electrode, constructed using Pseudomonas aminovorans grown on TMA, was sensitive to TMA, trimethylamine N-oxide (TMAO), dimethylamine (DMA) and monomethylamine (MMA). The second electrode responding to TMAO, DMA and MMA was prepared using Ps. aminovorans grown on TMAO. The difference in oxygen uptake was linearly related to the TMA concentration in the range of 5-26 microM. The minimum detectable level was 2.6 microM and the relative standard deviation was determined to be 14% for 16 repeated analyses. When operated and stored at 30 degrees C, the response of the system was stable for only 2 days. However, when the biosensor system was operated at 30 degrees C but stored overnight at 4 degrees C, the system was stable up to 20 days. The biosensor system was applicable for the determination of TMA in fish tissue extracts and the results compared well with those determined by HPLC.

Production and purification of L-phenylalanine oxidase from Morganella morganii.

An enzyme fraction, acting predominantly on L-phenylalanine has been purified and characterized from Morganella morganii. The total envelope was prepared by disrupting the cells with a French press followed by high speed centrifugation. After solubilization of the particulate fraction with 0.1% Triton X-100 and then centrifugation, the resulting supernatant was layered onto a DEAE-Cellulose column. Active fractions eluted were applied to a Phenyl-Sepharose CL-4B column as the final purification step. The activity of the purified enzyme to various L-amino acids in decreasing order was phenylalanine, methionine, leucine, tryptophan, and to a much lesser extent cysteine and tyrosine. At 4 degrees C in 20 mM phosphate buffer pH 7.5, the partially purified fractions collected from the DEAE-Cellulose column were stable for 120 h. On the other hand, the purified fractions obtained from the Phenyl Sepharose CL-4B column showed a drastic decrease in activity within only 24 h. Mg2+ (up to 40 mM), Mn2+ or Ca2+ (up to 10 mM) stimulated the oxidation of the purified enzyme but increases beyond such levels decreased the enzyme activity. Co2+ (0.05 mM), Cu2+ (0.5 mM) or Zn2+ (0.1 mM) decreased the enzyme activity 37, 33 and 20%, respectively.

Physiological study on riboflavin production by hydrocarbon-utilizing Candida guilliermondii Wickerham.

The production of riboflavin (vitamin B2) by Candida guilliermondii Wickerham cultivated on solar-containing medium was stimulated in the presence of corn oil (0.1 g%), arginine, phenylalanine (1 m mole/l) or CoSO4.7H2O (1000 micrograms/l). On the other hand, emulsifying agents strongly inhibited yeast growth and vitamin production. Similarly, FeSO4.7H2O and MnSO4.4H2O at 50 and 200 micrograms/l levels, respectively, also showed inhibitory effect. Among the tested purines, xanthine enhanced vitamin production.

Production of riboflavin (vitamin B2) by hydrocarbon-utilizing yeasts.

Candida guilliermondii Wickerham was found to be superior to the other yeasts tested for growth yields and riboflavin production when cultivated on different carbohydrate and hydrocarbon-containing media. Among the refined petroleum fractions and cheap hydrocarbons tested, solar was selected as a carbon source best suited for the fermentation process. The highest growth yield and riboflavin output (10.64 mg/100 ml) by C. guilliermondii Wickerham were achieved by placing aliquots of 20 ml medium (pH 6.0) in 100 ml Erlenmeyer flasks and incubating the inoculated medium at 30 degrees C for 14 days in the dark.

Riboflavin formation by mould fungi cultivated on hydrocarbon-containing media.

The potentiality of some mould fungi, isolated from petroleum sludge to produce riboflavin when grown on hydrocarbon-containing media was tested. Aspergillus terreus was found to be distinguished by its capacity to produce riboflavin when cultivated on the different culture media tested. It was able to grow more luxuriantly and produce good riboflavin output on solar-containing medium. A solar concentration of 5% v/v favoured high riboflavin productivity. The maximal vitamin B2 yields were achieved after 20 days incubation at 30 degrees C. An initial pH value of 5.5-6.0 was found to be the optimum for growth of A. terreus and for riboflavin production.