Alkaliphilic Microorganisms in Biotechnology

Abstract

Among extremophilic microorganisms, alkaliphiles are probably the least studied group despite they are diverse and serve as sources of many industrially important products. These organisms are normally found in environments characterized by high pH, but have also been isolated from non-alkaline environments. Alkaliphiles cover a broad range of organisms, some are just alkali-tolerant while others are strict alkaliphiles which grow optimally at or above pH 9 but do not thrive at neutral or acidic conditions. A wide variety of alkaliphiles have been isolated from different natural and man-made alkaline environments. The great majority comes from soda lakes and soda deserts, the most well-known are the lakes in the Great Rift Valley of East Africa and the salt lakes and salt deserts in western USA. These extremophiles use many adaptive mechanisms to survive in ‘extreme’ alkaline environment and some of these mechanisms are of great importance to a range of biotechnological applications. For instance alkaliphiles evolved enzymes that are operationally stable at high pH. Several applications require such enzymes that are active and stable at alkaline conditions. Some alkaliphiles decrease the severity of the high pH of their media by producing substantial amount of organic acids which implies that these organisms can be potentially used to produce organic acids. Organic acids are important inputs in many industrial processes. A number of other valuable novel products such as bioactive compounds, carotenoids and siderophores have also been reported from alkaliphiles, which will expand the application range of these organisms. In addition to their industrial biotechnology importance, alkaliphiles are of interest in environmental biotechnology such as in neutralizing alkaline waste and removing heavy metal contaminants. This chapter deals about the biotechnology of alkaliphiles and focuses on selected industrial applications of alkaline active enzymes, and briefly describes the biotechnological importance of these remarkable extremophiles in the production of carotenoids, siderophores, antibiotics and organic acids. Moreover, it discusses the potential of alkaliphiles in environmental applications with some examples.