Modeling herbivorous animal digestive system as 3- continuous stirred tank reactor (CSTR) and 1-plug flow reactor (PFR) in series with specific reference to Hippopotamus amphibious

Herbivores contain microflora in their guts which digest lignocellulosics in their stomachs and intestines by secreting the essential enzymes that perform the function so efficiently that the guts of these animals have been described as the best fermentation tanks known. Hippopotamus amphibious, a herbivorous animal, has three stomach compartments together with small and large intestines which are of similar structure and function. This work models each stomach compartment as continuousstirred tank reactor (CSTR) and the small and large intestines as plug flow reactor (PFR) arrangements in series in order to determine the performance of the herbivorous digestive system. Autocatalytic microbial fermentation takes place in the stomach, modeled as CSTR and described by Monod kinetics, whereas enzymatic digestion takes place in the intestines, modeled as PFR and described by Michaelis Menten equation. Designed equations derived from the two equations are used for the reactor sizing of the modeled reactors. This shows the efficiency of each reactor at converting the purely lignocellulosics substrates to useful products like protein, vitamin, fatty acid and the bye-products. The results showed that 3CSTR-IPFR model is the best and most efficient for converting lignocellulosics.Keywords: Lignocellulosics, microflora, herbivore, catalytic, reacto

Kinetics of batch microbial degradation of phenols by indigenous binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescence

The potential of various organisms to metabolize organic compounds has been observed to be a potentially effective means in disposing of hazardous and toxic wastes. Phenolic compounds have longbeen recognized as one of the most recalcitrant and persistent organic chemicals in the environment. The bioremediation potential of an indigenous binary mixed culture of Pseudomonas aeruginosa andPseudomonas fluorescence was studied in batch culture using synthetic phenol in water in the concentration range of 100 –500 mg/L as a model limiting substrate. The effect of initial phenol concentration on the degradation process was investigated. Phenol was completely degraded at different cultivation times for the different initial phenol concentrations. Increasing the initial phenol concentration from 100 to 500 mg/L increased the lag phase from 0 to 18 h and correspondinglyprolonged the degradation process from 24 to 96 h. There was decrease in biodegradation rate as initial phenol concentration increased. Fitting data into three different kinetic models (Monod, Haldane, andYano and Koga) showed that the difference in fit between the models was very small and thus statistically insignificant. Thus, the Yano and Koga model has been used to interpret the free cell dataon phenol biodegradation. The kinetic parameters have been estimated up to initial phenol concentration of 500 mg/L. The rsmax decreased, while Ks and Ki increased with higher concentration of phenol. The rsmaxhas been found to be a strong function of initial phenol concentration

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

Steady states of a continuous culture with an inhibitory substrate were used to estimate kinetic parameters under substrate limitation (chemo stat operation). Mixed cultures of an indigenous Pseudomonas fluorescence and Pseudomonas aeruginosa were grown in continuous culture on phenol as the sole source of carbon and energy at dilution rates of 0.01 – 0.20 h-1. 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 phenol degradation by mixed culture of P. fluorescence and P. aeruginosa can be described by simple substrate inhibition kinetics under substrate limitation but cannot be described by simple substrate inhibition kinetics under washoutcultivation. The phenol consumption rate (degradation rate) increased with increase in dilution rate. Fitting of the steady state data from continuous cultivation to six inhibition models resulted in the bestfit for Haldane, Yano and Koga, Aiba et al. and Teissier models, respectively. The rsmax value of 0.322 mg/mg/h obtained from these model equations was comparable to the experimentally calculated rsmax value of 0.342 mg/mg/h obtained under washout cultivation

Energetics of binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescence growth on phenol in aerobic chemostat culture

Bioenergetic analysis of the growth of the binary mixed culture (Pseudomonas aeruginosa and Pseudomonas fluorescence) on phenol chemostat culture was carried out. The data were checked for consistency using carbon and available electron balances. When more than the minimum number of variables are measured, and measurement errors are taken into account, the results of parameter estimation depend on which of the measured variables are chosen for this purpose. Similar parameter estimates were obtained using Pirt’s model based on the Monod equation approach and a modified model based on substrate consumption being rate limiting. Coupled with the covariate adjustmentestimation technique, the best estimates were the maximum likelihood estimates (MLE) based on when all the measured data were used. For the aerobic growth of the mixed culture on phenol, ηmax = 0.396 and me= −0.020 h-1. From the 95% confidence intervals, a maximum of about 38 – 41.3% of the energy contained in phenol is incorporated into the mixed culture biomass. The balance (58.7 – 62%) is evolved as heat with little or no energy needed for the maintenance of organisms.Keywords: Binary mixed culture, biomass energetic yield, chemostat culture, energetic analysis, maintenance coefficient, Pirt’s mode

Growth of Pseudomonas fluorescens on Cassava Starch hydrolysate for Polyhydroxybutyrate production

The potential of local strains of microorganism (Pseudomonas fluorescens) in polyhydroxbutyrate production was investigated in this study. This was with a view to establishing the capabilities of local strains of microorganisms on utilizing renewable and locally available substrates in polyhydroxybutyrate production. This involved hydrolysis of starch extracted from freshly harvested cassava tubers using enzyme-enzyme method of hydrolysis, followed by aerobic fermentation of Pseudomonas fluorescens on a mixture of the hydrolysate and nutrient media in a fermentor in batch cultures. The reducing sugar hydrolysate served as the carbon source and diammonium sulphate as the limiting nutrient. The reaction temperature, pH and agitation rate in the fermentor were maintained at 30°C, 7.5 and 400 rpm respectively. The biomass growth was measured by cell dry weight and the polyhydroxybutyrate content measured by gas chromatography. When the fermentation process was shut down after 84 hour, the substrate consumption by the organism was 9.2 g/L to give a dry cell weight of 1.75 g/L resulting in a biomass yield on substrate (Yx/s) of 0.1902 g/g (19.02 % wt/wt). The gas chromatographic analysis gave a final polyhydroxybutyrate value of 1.254 g/L with corresponding product yield on biomass (Yp/x) of 0.7166 g g-1 [71.66% wt/wt] and product yield on substrate (Yp/s) of 0.1363 g g-1 [13.63% wt/wt]. The results show that the organism accumulated polyhydroxybutyrate in excess of 50 % of the cell dry weight by giving a final polyhydroxybutyrate yield on biomass (Yp/x) of 0.7166 g g-1 [71.66% wt/wt] which agrees with the general trend in polyhydroxybutyrate production. @ JASEMJ. Appl. Sci. Environ. Manage. December, 2010, Vol. 14 (4) 61 - 6

Optimization of process variables for the microbial degradation of phenol by Pseudomonas aeruginosausing response surface methodology

Removal efficiency of phenol from aqueous solutions was measured using a freely suspended monoculture of indigenous Pseudomonas aeruginosa. Experiments were performed as a function of temperature (25– 45oC), aeration (1.0 – 3.5 vvm) and agitation (200 – 600 rpm). Optimization of these three process parameters for phenol biodegradation was studied. Statistically designed experiments using response surface methodology was used to get more information about the significant effects and the interactions between the three parameters. A 23 full-factorial central composite designed  followed by multistage Monte-Carlo optimization technique was employed for experimental design and analysis of the results. The optimum process conditions for maximizing phenol degradation (removal) were recognized as follows: temperature 30.1oC, aeration 3.0 vvm, and agitation 301 rpm. Maximum removal efficiency of phenol was achieved (94.5%) at the optimum process conditions

Homogeneously catalyzed transesterification of nigerian jatropha curcas oil into biodiesel: a kinetic study

As a follow-up to our previous study on the transesterification of Nigerian Jatropha curcas oil into Biodiesel using homogenous catalysis, kinetic study of the reaction is hereby presented. The kinetic study revealed that the rate of formation of biodiesel can be increased by increasing reaction temperature and oil to alcohol molar ratio. The optimum reaction condition was established to be 60˚C (reaction temperature) and 1:6 (oil to alcohol ratio). Accordingly, the highest biodiesel yield obtained from homogeneously catalyzed transesterification of Nigerian Jatropha curcas (JC) oil into Biodiesel was 86.61% w/w at 60˚C with oil to alcohol ratio of 1:6. Furthermore, kinetic study also revealed that conversion of triglyceride to diglyceride was the rate determining step (RDS) of the overall reaction because activation energy of its backward reaction is lower than that of the forward reaction, indicating unstable nature and higher potential energy of the diglyceride in comparison to the triglycerid