Application of Biopolymers in Problematic Soil improving

Biopolymers are the main components of the cell, generally consisting of 90 % of dry cell substance. They are combinations of several hundred or thousands monomers forming branching chain, chain, globular, or layered structure. The main cell monomers are amino acids, monosaccharides, and nucleotides, which are combined by covalent and other chemical bonds forming such polymers as proteins, polysaccharides, ribonucleic and deoxynucleic acids, respectively. Microbial cells produce extracellular polysaccharides, generally, exopolysaccharides, producing under an excess of energy and carbon sources and serving for cells as a store of carbon and energy and a supporter of cells from drying, antibiotics and heavy metals The main producers of these compounds are Gram-negative bacteria from the genera Alcaligenes and Xanthomonas but the spectrum of industrially present producers is continuously increasing.The advantage of microbial biopolymers is a high rate of these substances’ biosynthesis led to their simple production in industrial scale on biotechnological factories.The main applications of microbial extracellular polymers are using cement-based substances for dispersing, water retention, thickening, set retardation, film formation, and air entrainment The most commonly used microbial polymers in cement-based materials are welan, diutan, and xanthan gums.All microbial polymers are producing by the following steps: (1) preparation of microbial inoculum; (2) aseptic cultivation (3) removing of bacterial biomass (4) concentration of polysaccharides, generally by precipitation after addition of ethanol; (5) separation the precipitated polysaccharide (6) drying of the separated polysaccharide.Production of cement, a major construction material, is environmentally unfriendly and energy consuming. Energy represents 20-40% of the total cost of cement production because temperatures above 950 C are required for change of limestone to cement clinker In contrast to conventional cement production, microbial-based bio-cementing or bio-clogging materials have advantages over common cement and grouts, for example, sustainability due to their production from organic matter, and low risk of negative environmental consequences and low viscosity.

کلیدواژه ها:

Biocement ، Biopolymer ، Microbial cell ، Problematic soils