Biodegradation kinetics of o-cresol by Pseudomonas putida DSM 548 (pJP4) and o-cresol removal in a batch-recirculation bioreactor system

The biodegradation kinetics of o-cresol was examined by acclimatized P. putida DSM 548 (pJP4) in batch experiments at varying initial o-cresol concentrations (from 50 to 500 mg/L). The kinetic parameters of o-cresol aerobic biodegradation were estimated by using the Haldane substrate inhibition equation. The biodegradation kinetics of o-cresol was investigated. In batch culture reactors, the Maximum specific growth rate (μmax), Monod constant (Ks) and the inhibition constant (Ki) were established as 0.519 h-1, 223.84 mg/L and 130.883 mg/L, respectively. o-cresol biodegradation in a batch-recirculation bioreactor system by immobilized P. putida was also studied. The recycled packed bed reactor system, which was composed of Ca-alginate beads and pumice on which cells immobilized, has been performed to determine possible stability for further developments.

A Study on Urinary Excretion of o-Cresol and Hippuric Acid of Workers Daily Exposed to Toluene on Each Day of the Week / 항공우주의학회지

BACKGROUND: The purpose of this study is to find out the relationship between the airborne toluene concentrations and the daily urinary metabolites such as hippuric acid and o-cresol for a sequential 5 days and to provide the appropriate sampling time for a special physical examination in the workers exposed to toluene. METHODS: The volunteers of 36 workers in the shoe making company were selected to measure the concentrations of airborne toluene exposure and to sample the daily urines in pre and end-shift for sequential 5 days form Monday to Friday and to get self-administered questionnaire including the items such as job records, disease records, smoking, alcohol drinking, eating some foods containing benzoic acid before work. RESULTS: The geometric means of toluene concentrations showed 46.40 ppm as the lowest value on Monday and 62.31 ppm as the highest one on Thursday. But there is no significant difference between both of those. The concentrations of hippuric acid and o-cresol in urine sampled on end-shift were higher than that of the others and showed statistically significant differences on each day. The metabolites of toluene were not related with taking alcohol and some foods containing benzoic acid as a result of logistic regression. CONCLUSION: From the above results, it is suggested that the hippuric acid and o-cresol in urine be very useful for biological monitoring in the workers exposed to toluene. Moreover, the daily hippuric acid and o-cresol concentrations in urine are also important for toluene exposure assessment and the further study has to be conducted to find out the tendency of biological exposure indices for continuous toluene exposure.

A Study on the Correlation of Ambient Toluene and Xylene with Biological Monitoring Index / 대한산업의학회지

In order to study the correlation of ambient toluene and xylene exposure with their biological monitoring indices, we measured the concentration of toluene and xylene in the workplace. We also measured their biological monitoring indices of workers from August to November in 1994. The exposed group consisted of 103 male workers and the non-exposed group consisted of 34 male workers. The ambient concentration of toluene was 44.7 +/-55.4 ppm and that of xylene was 2.35+/-2.15 ppm. The urinary concentration of hippuric acid in exposed group was 1.72+/-1.53 g/g creatinine and that of non-exposed group was 0.34+/-0.28 g/g creatinine. The difference was statistically significant between two groups (p0.05). When compensated with urinary creatinine, the correlation coefficient of ambient toluene with urinary hippuric acid and ocresol were 0.63(p=0.0001) and 0.65(p=0.0001), respectively. When compensated with urinary specific gravity, the correlation coefficient of ambient toluene with hippuric acid and ocresol were 0.525 (p=0.0001) and 0.547 (p=0. 0001), respectively. The compensation method using urinary creatinine provided a higher correlation coefficient. We could not find any statistically significant differences between the duration of work and other variables (urinary hippuric acid, o-cresol and methylhippuric acid). In order to monitor biological indices of toluene-exposed workers, we suggest the measurement of urinary hippuric acid rather than o-cresol. As the compensation method, we suggest to use urinary creatinine rather than urinary specific gravity.