Bamidele O. Solomon

Production of Polyhydroxyalkanoates, a bacterial biodegradable polymer

There has been considerable interest in the development and production of biodegradable polymer to solve the current problem of pollution caused by the continuous use of synthetic polymer of petroleum origin. Polyhydroxyalkanoates (PHAs) are known to be accumulated as intracellular inclusion in some bacteria. The materials properties exhibited by PHAs, ranging from stiff, brittle to rubber-like makes it a close substitute for the synthetic plastic. The high cost of PHAs production has restricted its applications. The possibility of producing this polymer commercially and at comparable cost has been the main focus in this area. Key Words: Polyhydroxyalkanoates, biodegradable polymer, bioplastic, poly(3-hydroxybutyrate), biosynthesis. African Journal of Biotechnology Vol.3(1) 2004: 18-24

Substrate inhibition kinetics of phenol degradation by Pseudomonas fluorescence from steady state and wash-out data

The present study investigated the phenol utilization kinetics of a pure culture of an indigenous Pseudomonas fluorescence under steady state and non-steady state (washout) conditions. Steady states of a continuous culture with an inhibitory substrate was used to estimate kinetic parameters under substrate limitation (chemo stat operation) Pure cultures of an indigenous Pseudomonas fluorescence were grown in continuous culture on phenol as the sole source of carbon and energy at dilution rates of 0.010 - 0.20/h. Using different dilution rates, several steady states were investigated and the specific phenol consumption rates were calculated. In addition, phenol degradation was investigated by increasing the dilution rate above the critical dilution rate (washout cultivation). The results showed that the specific phenol consumption rate increased with increased dilution rate at steady state and phenol degradation by Pseudomonas fluorescence can be described by simple substrate inhibition kinetics under substrate limitation but cannot be described by simple substrate inhibition kinetics under washout cultivation. Fitting of the steady state data from continuous cultivation to various inhibition models resulted in the best fit for Haldane, Yano and Koga (2), Aiba and Teissier kinetic inhibition models. The rsmax value of 0.229 mg/mg/h obtained from the inhibition model equations was comparable to the experimentally calculated rsmax value of 0.246 mg/mg/h obtained under washout cultivation. Therefore, the biokinetic constants evaluated using these models showed good tolerance and growth of the indigenous organism.

Biodegradation of phenol in refinery wastewater by pure cultures of Pseudomonas aeruginosa NCIB 950 and Pseudomonas fluorescence NCIB 3756

The potential of microorganisms to catabolise and metabolise xenobiotic compounds has been recognised as a potentially effective means of toxic and hazardous wastes disposal. Phenol and its derivatives have long been recognised as some of the most persistent chemicals in petroleum refinery wastewaters, with high toxicity even at low concentrations. Biodegradation of these compounds has been recognised as a potential solution for their disposal owing to its cost effectiveness and simplicity. Two species of pseudomonas, P. aeruginosa and P. fluorescence, were studied for their biodegradation potential on phenol present in a refinery wastewater under a batch fermentation process. Phenol was successfully degraded by both species, and there was high positive correlation between phenol biodegradation and microbial growth. The maximum specific growth rate were obtained for both species from the Haldane model. The study revealed the high potential of these local strains, with P. aeruginosa being more effective, and the possibility of using them in bioremediation of petroleum refinery wastewaters.

Analysis of the respiro-fermentative growth of Saccharomyces cerevisiae on glucose in a fed-batch fermentation strategy for accurate parameter estimation

Analysis of the respiro-fermentive growth of a strain of Saccharomyces cerevisiae, DSM 2155 on glucose, in a simulated 5-phase feeding strategy of fedbatch cultures executed on the Universal BIoprocess CONtrol (UBICON) system, was carried out. There was a good agreement between the estimated and the simulated values of specific growth rates. In this study, which was designed to span 0.20–0.23 h−1 growth rates before returning to lower growth rates, the critical dilution rate at which the switch between purely oxidative and respiro-fermentative growth takes was not observed. The biomass yield, specific substrate uptake and O2 consumption rates as well as the consistency of the data using both carbon and available electron balances were examined. A high average value of true biomass energetic yield, ηmax = 0.707, and a low value of maintenance coefficient, me = 0.0114 h−1, were obtained indicating that the organism was in no danger from the ethanol produced as a high-density fermentation with a yeast concentration above 54 g 1−1 was possible within a period of 24 h. The yeast produced also had good dough-leavening characteristics. Thus it is possible to operate a yeast plant without resorting to using respiratory quotient, which may be problematic, as the controlling parameter.

A comparative study of the hydrolysis of gamma irradiated lignocelluloses

The effect of high-dose irradiation as a pretreatment method on two common lignocellulosic materials; hardwood (Khaya senegalensis) and softwood (Triplochiton scleroxylon) were investigated by assessing the potential of cellulase enzyme derived from Aspergillus flavus Linn isolate NSPR 101 to hydrolyse the materials. The irradiation strongly affected the materials, causing the enzymatic hydrolysis to increase by more than 3 fold. Maximum digestibility occurred in softwood at 40kGy dosage of irradiation, while in hardwood it was at 90kGy dosage. The results also showed that, at the same dosage levels (p < 0.05), hardwood was hydrolysed significantly better compared to the softwood.

Auto-hydrolysis of lignocellulosics under extremely low sulphuric acid and high temperature conditions in batch reactor

Batch reactors were employed to investigate the kinetics of cellulose hydrolysis under extremely low acid (ELA) and high temperature condition. The sawdust was pretreated by Autohydrolysis prior to the batch reaction. The maximum yield of glucose obtained from the batch reactor experiment was about 70% for the pretreated sawdust, this occurred at 210 and 220°C. The maximum glucose yield from the untreated sawdust was much lower at these temperatures, about 55%. The maximum yields of glucose from the lignocellulosics were obtained between 15th and 20th minutes after which gradual decrease was observed.

Fermentation parameter optimization of microbial oxalic acid production from cashew apple juice

The potential of cashew apple juice (CAJ) as a carbon source for oxalic acid (OA) production via fermentation process was investigated in this study. The effects and interactions of CAJ concentration, time, pH, NaNO3 concentration and methanol concentration on OA production were determined in a central composite design (CCD) and the process was modelled and optimized using response surface methodology (RSM). The results showed that OA fermentation can be described significantly (p < 0.05) by a quadratic model giving regression coefficient (R2) of 0.9964. NaNO3 concentration was the most significant positive variable while methanol was not a significant variable. A maximum OA concentration of 122.68 g/l could be obtained using the optimum levels of CAJ of 150.0 g/l, pH of 5.4, time of 7.31 days, NaNO3 of 2 g/l and methanol of 1% volume. The production of OA was found to increase from 106.75 to 122.68 g/l using the statistically design optimization. This study revealed that CAJ could serve as an inexpensive and abundant feedstock for fermentative OA production, the resulting model could be used in the design of a typical pilot plant for a scale up production.

KINETIC MODELLING AND HALF LIFE STUDY OF ADSORPTIVE BIOREMEDIATION OF SOIL ARTIFICIALLY CONTAMINATED WITH BONNY LIGHT CRUDE OIL

In this study, comparative potential effects of commercial activated carbon (CAC) and plantain peel-derived biochar (PPBC) of different particle sizes and dosage to stimulate petroleum hydrocarbon biodegradation in soil were investigated. Microcosms containing soil were spiked with weathered Bonny light crude oil (WBLCO) (10% w/w) and amended with different particle sizes (0.02, 0.07 and 0.48 mm) and dosage (20, 30 and 40 g) of CAC and PPBC, respectively. The bioremediation experiments were carried out for a period of 28 days under laboratory conditions. The results showed that there was a positive relationship between the rate of petroleum hydrocarbons reduction and presence of the CAC and PPBC in crude oil contaminated soil microcosms. The WBLCO biodegradation data fitted well to the first-order kinetic model. The model revealed that WBLCO contaminated-soil microcosms amended with CAC and PPBC had higher biodegradation rate constants (k) as well as lower half-life times (t1/2) than unamended soil (natural attenuation) remediation system. The rate constants increased while half-life times decreased with decreased particle size and increased dosage of amendment agents. ANOVA statistical analysis revealed that WBLCO biodegradation in soil was significantly (p = 0.05) influenced by the addition of CAC and biochar amendment agents, respectively. However, Tukey’s post hoc test (at p = 0.05) showed that there was no significant difference in the bioremediation efficiency of CAC and PPBC. Thus, amendment of soils with biochar has the potential to be an inexpensive, efficient, environmentally friendly and relatively novel strategy to mitigate organic compound-contaminated soil.

A comparison of the efficacy of two strains of Bacillus subtilis and Pseudomonas fragii in the treatment of tannery wastewater

Abstract Tannery wastewater treatment using two isolated micro-organisms (Bacillus subtilis and Pseudomonas fragii) has been investigated in the present study. The growth patterns, pH normalisation and the abilities of these micro-organisms to reduce the concentrations of chemical oxygen demand (COD), total suspended solids (TSS) and chloride were studied using the shake flask apparatus. The specific growth rate and biomass concentration of B. subtilis and P. fragii were observed 0.138 h−1 and 3.01 mg/l and 0.051 h−1 and 2.34 mg/l, respectively, after 84 h. Both micro-organisms normalised pH of the wastewater. COD removal efficiency for B. subtilis was 87.6% while that of P. fragii was 85.2%. For TSS, B. subtilis caused a reduction of 91.7% (from 876 mg/l to 73 mg/l), while P. fragii reduced the solid concentration from 876 mg/l to 98 mg/l (88.8%). B. subtilis could only achieve 48.5% reduction in chloride concentration (from 127.08 mg/l to 65.39 mg/l compared to a reduction of 54.6% (from 127.08 mg/l to ...

Data consistency, yield and maintenance coefficient for the growth of Candida lypoytica and Pseudomonas aeruginosa on n-hexadecane

SummaryWhen more than the minimum number of variables are measured, and measurement error is taken into account, the results of parameter estimation depend on which of the measured variables are selected for this purpose. The reparameterization of Pirts models for growth produces multiresponse models with common parameters. By using the covariate adjustment technique, a unit variate linear model with covariates is obtained. This allows a combined point and interval estimates of biomass energetic yield and maintenance coefficient to be obtained using standard multiple regression programmes. When this method was applied using form I and form II of the Pirts models, good combined estimates were obtained and compared. Using data from the literature for Candida lipolytica produced reliable results. However, for Pseudomonas aeruginosa, which has been known to produce intermediate products, a modified Pirts model is required for a good estimate of the biomass energetic yield.