Potential Biotechnological Applications of Cyanobacterial Exopolysaccharides

Abstract The cyanobacterial exopolysaccharides (EPSs) are considered as one of the important group of biopolymers having significant ecological, industrial, and biotechnological importance. Cyanobacteria are regarded as a very abundant source of structurally diverse, high molecular weight polysaccharides having variable composition and roles according to the organisms and the environmental conditions in which they are produced. Due to their structural complexity, versatility and valuable biological properties, they are now emerging as high-value compounds. They are possessing exceptional properties and thus are being widely explored for various applications like in food and pharmaceutical industries, in bioremediation for removal of heavy metals, for soil conditioning, as biopolymers, bioadhesives, and bioflocculants. However, poor understanding of their complex structural properties, lack of concrete information regarding the genes encoding the proteins involved in the EPS biosynthetic pathways, their process of production and about the associated factors controlling their structural stability, strongly limits their commercialization and applications in the various fields of biotechnology. Owing to the above context, the present review is aimed to organize the available information on applications of cyanobacterial EPSs in the field of biotechnology and to identify the research gaps for improved industrial utilization and commercialization of these biomaterials.

Exopolymers from Tolypothrix tenuis and three Anabaena sp. (Cyanobacteriaceae) as novel blood clotting agents for wound management.

Rapid initiation of clotting is critical to trauma patients. In the present study exopolymers (EPs) from four desert cyanobacteria including Tolypothrix tenuis and three species of Anabaena have been discovered as potential hemostatic biomaterials. The EPs showed reduction in activated partial thromboplastin time (APTT) and prothrombin time (PT) by 16-41% and 12-65%, respectively. Besides hastening blood clotting, the EPs could absorb 7.1-25.9 g H2O g(-1) EP and displayed 7.1-18.1% hydrophobicity. They were noncytotoxic and biodegradable. The EP from Anabaena sp. showed strong antibacterial activity against E. coli, S. aureus and B. licheniformis. These results suggest that cyanobacteria, the microscopic phototrophs growing rapidly over simple mineral medium could prove to be a novel source of affordable hemostatic dressings for the traumatic wounds in underdeveloped and developing countries. Compositional analysis of the EPs showed them to be consisting of mainly carbohydrate (17-50%), protein (4.4-7.2%), uronic acid (4.7-9.5%) and sulphate (0.6-6.6%). Their viscometric molecular weight ranged from 539 to 3679 kDa. They were further characterized using GC-MS and FTIR.

Hemostatic, antibacterial biopolymers from Acacia arabica (Lam.) Willd. and Moringa oleifera (Lam.) as potential wound dressing materials.

Acacia arabica and Moringa oleifera are credited with a number of medicinal properties. Traditionally gum of Acacia plant is used in the treatment of skin disorders to soothe skin rashes, soreness, inflammation and burns while Moringa seed extracts are known to have antibacterial activity. In the present study the potential of the polymeric component of aqueous extracts of gum acacia (GA) and the seeds of M. oleifera (MSP) in wound management was evaluated. The results revealed that both biopolymers were hemostatic and hasten blood coagulation. They showed shortening of activated partial thromboplastin time and prothrombin time and were non-cytotoxic in nature. Both showed antibacterial activity against organisms known to be involved in wound infections with MIC ranging from 500-600 microg mL(-1) for GA and 300-700 microg mL(-1) for MSP. They were biodegradable and exhibited water absorption capacity in the range of 415 to 935%. The hemostatic character coupled to these properties envisions their potential in preparation of dressings for bleeding and profusely exuding wounds. The biopolymers have been further analysed for their composition by Gas chromatography.