Caffeine is an important naturally occurring compound that can be degraded by bacteria. Excessive caffeine consumption is known to have some adverse problems. Previously, Leifsonia sp. strain SIU capable of degrading caffeine was isolated from agricultural soil. The bacterium was tested for its ability to degrade caffeine as the sole carbon and nitrogen source. The isolate was encapsulated in gellan gum and its ability to degrade caffeine in the presence of heavy metals was determined. Out of the nine heavy metals tested, Copper (Cu), Mercury (Hg), and Silver (Ag) had significant effects on caffeine degradation at 1mg/L. Therefore, the concentration of these heavy metals was varied from 0 -1 mg/L to see at what concentration each metal it has effect. Ag and Hg showed effect at 0.1 mg/L with caffeine degradation of 64.05 and 52.17% respectively, while Cu showed effect at 0.8 mg/L with caffeine degradation of 64.74%. These bacterium features make it an ultimate means for caffeine bioremediation. This is the first report of effect of heavy metals on caffeine degradation by immobilised Leifsonia sp. strain SIU.
Tributyltin (TBT) is one of the most toxic substances ever deliberately introduced into the marine environment. The high toxicity of TBT has resulted in a wide range of adverse effects on biological systems ranging from bacteria to mammals and from the molecular to the community level. One of the most deleterious effects of TBT is imposex. The growth kinetics of TBT-Resistant Bacterium containing lead was studied. In this study various lead concentrations ranging from 1 to 100 mg/dm 3 were used. Seven kinetic models (Teissier, Monod, Yano, Luong, Aiba, Webb, and Haldane,) were investigated and the accuracy of the fitted models were evaluated using statistical analysis such as coefficient of determination, adjusted coefficient of determination (R 2 ) and root mean square (RMSE). Aiba model was fitted to the experimental growth kinetics data and gave a very good fit with an R 2 of 0.98 and RMSE of 0.0042 respectively. The calculated value for the Aiba constants such as maximal growth rate, half saturation constant and half inhibition constant rate symbolized by µ max , k s , and k i , were 0.
Abstract:This study designed to enhance the nutritional quality of corn mill waste (CMW) with microbial protein accumulated during submerged fermentation by selected microbial consortium. CMW is the dry, scaly residue of milled corn seed popularly known as chaff. A slurry prepared from a mixture of 1: 2 ratio of CMW and hot water (80 -95°C) supplemented with mineral salts were fermented for 7 days with microbial consortium (Candida utilis, Aspergillus niger and Saccharomyces cerevisiae) as starter culture. During fermentation, microbial and physicochemical (pH, temperature and titratable acidity) profile were evaluated. Nutritional composition and preliminary acute toxicity of the dried fermented CMWs were assayed. Results showed that starter culture (67.7%) and non-starters (33.3%) persisted in the 7-days fermentation. Titratable acidity and pH decreased by 34.5% and 11.1% respectively, unlike temperature that was relative stable during fermentation. Protein content were significantly increased (74%); while total carbohydrate decreased (25%) after fermentation. Fermented CMW had no significant (P<0.05) acute and subacute toxic impact on birds. There were slight but no significant difference (P<0.05) on nutritional composition and cost index of fermented CMW and commercial feed (control). Conclusively, Fermented CMW offer a prospective economic alternative as poultry feed for rural regions with abundant CMWs.
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