Isolation and Characterization of Pigment Producing Bacteria from Soil and Conditions Optimizations for Its Production

Abstract

Different group of microbes, including bacteria, yeasts, mold, and algae, are found to produce pigments. The main aim of this thesis was to isolate and characterize pigment producing bacterial isolates from soil and optimization of conductions for the pigment production. The soil samples were collected and serially diluted from 10-1 to 10-6 and each dilution was plate on the sterilized nutrient agar, soya bean agar, and GMTYEA then incubated at 28°C under aerobic condition. From the different soil samples studied, two bacteria isolates Yellow from grassland and Red from root of mokanisa were selected for further investigation. After 48hrs of incubation yellow and red pigmented bacteria isolate were picked and purified by repeated streaking on DA and the pure culture was maintained on slant DA at 4°C. Both extracellular and intracellular pigments obtained from the bacterial isolates were analyzed by using UV visible spectrophotometer. Effect of carbon sources, nitrogen sources, pH, incubation temperature and effect of salt concentrations on growth and pigment production were evaluated. The morphological and biochemical characterization of the bacterial isolates tentatively suggested as Serratia and Pseudomonas. From the different carbon sources tested starch and cellulose favored maximum extracellular (OD 3+0.65) and intra cellular (OD 2.799+0.23) red pigmentation while sucrose was found minimal extracellular and intracellular (1.25+0.13) and (1.23+0.66) but for yellow sorbitol was minimum (2.06+0.23) in this respect. For both bacterial isolates yeast extract (OD 0.376+0.81) enhanced more growth and pigmentation and for Yellow (OD 3+0.23). The optimum pigmentation of red bacterial isolates was at 28°C with OD value of (1.413+0.71) at 535nm. The optical density of the pigment of both bacterial isolates was higher around neutrality (pH 7) the pigmentation was gradually decline toward alkaline and acidic pH. Lower salt concentration was found to favor the growth and pigmentation, while increased salt concentration were found to be limiting. The optical density of the red bacterial isolate was increase with increase incubation period. The results of this study clearly indicated that the bacteria isolated from soil is able to produce different colored pigments under different nutritional and xiii environmental conditions suggesting that this bacterial isolates will be considered as a candidate for the industrial production of pigments which will be applied in various industries.