MICROBIAL BIOFILMS AS BIOFERTILIZERS

Microbial biofilms find application in various industries from health, agriculture to biotechnology.In natural environments, majority of microorganisms exist in polysaccharide encased consortium referred to as Biofilms.Biofilms form microbial communities comprising bacteria, fungi algae and so on which irreversibly attach to biotic or abiotic supporting materials fostering adaptation and tolerance to different microenvironmental conditions.Generally, most biofilms are made of extracellular polymeric substances (EPSs) which is a combination of several proteins, polysaccharides, lipids and nucleic acids [1].Microbial biofilms with beneficial attributes have been studied mostly in the area of environmental biotechnology; bioremediation, bioaugmentation, purification of water and recovery of resources [2].However there has been more study recently on the agrobiotechnological application of microbial biofilm especially in its use as biofertilizers.Considering the growing population around the world, production of an adequate amount of food is a major challenge.The United Nations Population Fund (UNFPA) estimates that the world population will increase to 9.7 billion in 2050 and 11.2 billion by 2100 [3].In the developing countries, agricultural production involves the use of chemical fertilizers, which causes a diverse change in soil pH, contributing to greenhouse gases, upset of the ecosystems of beneficial microbes, and further leaches into the groundwater which often times damages aquatic life.Further, in these countries, areas of forest have been turned into commercial lands for housing and industrial purposes, causing a large threat to global biodiversity [4].To foster sustainable agriculture and increase crop production ultimately ensuring food security more emphasis has been placed on retaining the fertility of soil through the use of biofertilizers [5].Biofertilizer are made of live formulations of microbes that possess growth-promoting traits, such as biological nitrogen fixation, solubilization of phosphorus, synthesis of various growth hormones, Iron-chelating compounds, hydrolytic enzymes, hydrogen cyanide (a biopesticide) and ammonia [6].Biofilm bio-fertilizer is prepared by assembling suitable microorganisms in vitro.The matrix on which these agents are embedded should be firmly fixed with barrier against UV light and should enhance enzymatic actions.Microorganisms used in biofilm production are selected on the basis of their resistance to antibiotics.Preparation of biofilm bio-fertilizer involves four steps [5].First is the bacterial attachment to substrate by adhesive force followed by rapid multiplication of micro-organisms resulting in formation of micro-colony.Transcription of specific genes of the intercommunicating bacterial cells then takes place resulting in EPS production.Increasing thickness of the EPS stimulates