The efect of acid and osmotic stress onmetabolite production by microorganisms

The efficiency of the overall biotechnological processes is strongly dependent on the interaction between the microbial biocatalyst and the stressful environment. Microorganisms have evolved to survive constant fluctuation in their external surroundings by special adaptation systems, including the reorganization of genomic expression by activation of transcriptional factors under stress conditions and the production of suitable metabolites. There is some evidence that more active microbial cells may be obtained by using abiotic stresses, such as osmotic and acidic stress, before or during the process. Also, changes in the conditions of stress application, for example its duration or simultaneous increase in temperature, may improve the yield, probably as a result of changes in the metabolic pathway of the microorganisms used. In this review, we have summarized the most important information from available literature on the effect of acid and osmotic stress on the production of useful metabolites by microorganisms. 1. Introduction. 2. Abiotic stresses. 2.1. Acidic stress. 2.2. Osmotic stress. 3. Conclusions