Showing papers by "Sathyanarayana N. Gummadi published in 2014"

Bioconversion of Non-Detoxified Hemicellulose Hydrolysates to Xylitol byHalotolerant Yeast Debaryomyces nepalensis NCYC 3413

Abstract: Lignocellulosic materials are one of the most abundant renewable resources whose exploitation for the production of biochemicals and biofuels is the major challenge in the area of industrial biotechnology due to inhibition of growth and product formation by the toxic compounds released upon their hydrolysis. Indeed the bioprocess that can produce industrial products from hemicellulose hydrolysates in the presence of toxic compounds is economical than the process which involves detoxification. In this study, the ability of halotolerant strain Debaryomyces nepalensis NCYC 3413 to convert non-detoxified xylose enriched hemicellulose hydrolysates from corn cobs, rice straw, sugarcane bagasse and wheat straw to xylitol was evaluated. It was found that this strain has the capability to grow in all hemicellulose hydrolysates and convert xylose to xylitol without detoxification of hydrolysates. The maximum xylitol concentration of 14.6 g L-1 was obtained from corn cobs and wheat straw with productivities of 0.16 and 0.20 g L-1 h-1 respectively at a yield of 0.30 g g-1. Whereas sugarcane bagasse and rice straw gave xylitol yields of 0.31 and 0.32 g g-1 respectively with 14.2 g L-1 maximum xylitol and productivities were calculated to be 0.20 and 0.15 g L-1 h-1 respectively. The presence of high glucose hindered xylitol production by producing ethanol. Based on our findings, we suggest that (i) D. nepalensis is a promising strain for ecofriendly xylitol production as it exhibits broad specificity to lignocellulose substrates, fermentation of mixed sugars and (ii) tolerance towards lignocellulosic inhibitors making the process more economical.

Optimization of Process Conditions for Biotransformation of Caffeine to Theobromine using Induced Whole Cells of Pseudomonas sp

Abstract: The obromine is a metabolic intermediate produced in caffeine degradation pathway by many bacterial species, which has potential applications in food and pharmaceutical industries. Conventional methods of Theobromine production from xanthine involve harsh physical and chemical conditions which are harmful to the environment. To overcome this, we employed biotechnological route to convert caffeine to theobromine by single demethylation reaction using induced cells of Pseudomonas sp. Initially we screened various divalent metal ions for the production of Theobromine by Pseudomonas sp. from caffeine. Co2+ and Ni2+ accumulates 400 and 100 mg/l of theobromine under initial reaction conditions (2 g/l caffeine, 8 g/l cell loading, pH 7.0,30°C). Co2+ was chosen for further optimization of reaction conditions for Theobromine production using response surface methodology. Data were fitted into a quadratic model and the optimal condition for theobromine production was found to be 3.2 g/l caffeine, 11.3 g/l initial cell loading and pH 7.0. Quadratic regression models were validated at the optimized conditions and the experimental theobromine produced 689.7 mg/l corresponds to the model predicted theobromine 729.4 mg/l. Theobromine production was further improved to 1.08 ± 0.10 g/l by optimizing the reaction temperature. This study reports highest production of theobromine from caffeine using induced cells of Pseudomonas sp. Induced cells are better suited for metabolite production as it is metabolically very active and can be re-used several times. Optimization of reactor parameters will enable us to make microbial production of theobromine feasible in industries at reduced cost.