Cost-effective production of biological materials for food applications

Abstract

This thesis consists of two chapters; in the first chapter response surface optimization of the production of a potential probiotic strain was studied by using bioreactors and in the second chapter screening of biosurfactant producing microorganisms was carried out followed by the purification and characterization of the biosurfactant produced. Probiotics are live microorganisms that when administered in adequate amounts are favorable to their host. They are used on livestock to enhance the growth of animals, improve the efficiency of feed conversion and to decrease mortality rate. Therefore, it is important to produce these microorganisms in high amounts. However, process economics is a problem in large scale production of the microorganisms. Main factors that affect the process economics are the growth medium of the organism and the process conditions. Therefore, optimizing the composition of the growth media and cultivation conditions are of crucial importance in large scale production. In this study, optimization of growth media composition and cultivation conditions of a novel probiotic strain, Bacillus pumilus STF26, was done. Factors optimized were temperature, pH and the concentrations of dextrose as carbon source, yeast extract as nitrogen source, KH2PO4 and MgSO4.7H2O. Response surface methodology was used to optimize the parameter and the optimum values are found to be 30.9 °C, 6.9, 20 % (w/v), 1.526 % (w/v), 0.1 % (w/v) and 0.5 % (w/v) for temperature, pH and the concentrations of dextrose, yeast extract, KH2PO4 and MgSO4.7H2O, respectively. Maximum biomass at optimum conditions was 10.42 g/L which is nearly 2.5 times higher when compared to the one obtained by using LB medium at optimized temperature and pH values. In the second chapter, production and characterization of a biosurfactant produced by a novel strain of Staphylococcus xylosus, STF1, was studied. Biosurfactants are surface active agents that have a broad range of applications in different industries and they have several advantages over their chemically synthesized counterparts. However, they cannot compete economically with synthetic surfactants due to their high production cost, the difficulties in downstream processing and the lack of overproducing strains. In this study a novel strain that produces biosurfactant, STF1, was isolated and the biosurfactant was characterized by using mass spectrometry and Fourier transform infrared (FTIR) spectroscopy. FTIR results indicated the lipopeptide nature of the biosurfactant produced by this strain. Moreover, the mass of the purified biosurfactant was 931.9550 (m/z).