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

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

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

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