Microbial diversity in freshwater ecosystems and its industrial potential

Abstract

Abstract Microbial diversity in freshwater ecosystem is predominated by Cyanobacteria (blue-green algae), a large and morphologically diverse group of Gram-negative photosynthetic prokaryotes which occur almost in every habitat on earth. Both free-living and endosymbionts have been found. Microalgae, the other dominant microbial group in freshwater, consists of prokaryotic or eukaryotic photosynthetic microorganisms that can grow rapidly and live in harsh conditions due to their unicellular or simple multicellular structure. The freshwater algae having microscopic appearance includes: green algae (Chlorophyta), Euglenoids, Xanthophyta, Dinoflagellates, Cryptophyta, Chrysophyta, Diatoms, Bacillariophyta, Rhodophyta, and Brown algae. The microalgae are the most promising sources of natural carotenoids and other compounds, such as fats, polyunsaturated fatty acids, oil, natural dyes, sugars, pigments, antioxidants, high-value bioactive compounds, and other fine chemicals. Cyanobacteria are basically microscopic, although large colonies or mats are quite conspicuous. Microbial mats are considered to be natural ecosystems that produce gases like CO2, CH4, H2, thereby promoting the potent use of gases, primarily produced by Cyanobacteria as biofuels. Their possible use in aquaculture; food; feed; fuel; fertilizer; colorant; production of various secondary metabolites including vitamins, toxins, enzymes, pharmaceuticals, pharmacological probes; and pollution abatement has given rise to the branch of algal biotechnology. This chapter highlights the commercial applications of Cyanobacteria as well as microalgae, discussing the challenges that need to be addressed to make cyanobacterial industrial biotechnology more feasible in near future.