Industrial wastewater as raw material for exopolysaccharide production by Rhizobium leguminosarum

The objective of this study was to evaluate the exopolysaccharide (EPS) production by Rhizobium leguminosarum cultivated in wastewater generated by oil companies (WWOC1 and WWOC2) and fish processing industry (WWFP). The results obtained in Erlenmeyer flasks indicated that the rhizobial strain grew well in industrial wastewater. Generally, wastewater composition affected the growth and the EPS production. WWFP allowed good bacterial growth similar to that obtained with the standard medium (YMB). During growth, various quantities of EPS were produced and yields varied depending on the media. Growing in YMB, EPS production did not exceed 9.7 g/L obtained after 72 h of growth. In wastewater, the maximum EPS value reached 11.1 g/L obtained with the fish processing wastewater, after 72 h of growth. The use of a mixture of the oil company wastewater (WWOC2) and the fish processing wastewater (WWFP) as culture medium affected not only the rhizobial strain growth, but also EPS production. The highest EPS (42.4 g/L, after 96 h of culture) was obtained using a ratio of WWFP and WWOC2 of 50:50 (v:v). Therefore, this work shows the ability of Rhizobium leguminosarum, growing in industrial wastewater as new economic medium, to produce EPS. This biopolymer could be applied in enormous biotechnological areas.

Host plant nodule parameters associated with nitrogen fixation efficiency in French bean (Phaseolus vulgaris L) cultivars.

Two cultivars of French bean (Phaseolus vulgaris L.) viz. contender and arka komal were planted in polythene bags containing sand and grown under glasshouse conditions. The nodulation status, shoot/root biomass, activities of several nodule enzymes, total soluble protein and leghaemoglobin contents were monitored over the entire growth period. Allantoinase activity in leaves was measured to monitor the ureide degrading capacity. Significant genotype difference was observed in both the cultivars. All the parameters showed a decline after flowering except uricase, which declined before flowering. Malate dehydrogenase and isocitrate dehydrogenase showed a constant decline throughout the growth period. Degree of decline varied with the genotype for all the parameters. Leghaemoglobin content, PEP carboxylase activity and ureide degrading capacity of leaves did not show an appreciable decline in contender and were significantly higher than in arka komal. These factors can be used to increase nitrogen fixation in French bean.