ICAR Research Data Repository for Knowledge Management

There is a worldwide concern regarding the development of biodegradable plastic materials as a remedy towards harmful effects caused by plastic wastes
on the environment. These materials, which are synthesized chemically by polymerization, contribute towards air pollution and waste management problems. The fear of depletion of wood resources has established plastics as
the material of choice in many applications. In food sector, various characteristics of plastics such as low density, ready sealability, resistant to break, appearance,
impermeability to oxygen and water vapor, low temperature and flexibility have contributed for its large usage. Unfortunately, these highly durable, versatile and
extremely useful material led to adverse effects on the environment after its use. Moreover, as over 99% of plastics are fossil fuel origin, their rapid increase will
put further pressure on the already limited non-renewable resources on earth. Plastics are not biodegradable and there is no concerted effort for plastic waste management.
All this has promoted worldwide research to develop new biodegradable alternatives to plastics. Amidst the pro plastic arguments, there still is a strong need for the look out for alternatives for synthetic plastics and to replace them steadily. Biodegradable polymers or bioplastics are important and interesting areas that are being looked out as alternatives for synthetic plastics. These are a new generation of materials able to significantly reduce the environmental impact in terms of energy consumption and green house effect. Polyhydroxyalkanoates (PHA)are microbial polyesters. These polymers have properties similar to synthetic plastics and in addition are biodegradable and biocompatible. Polyhydroxyalkanoates in particular are attractive ubstitutes for conventional petrochemical plastics because of their similar material properties to various thermoplastics and elastomers and their complete degradability upon disposal in various environments. Polyhydroxyalkanoates are synthesized by numerous bacteria as intracellular carbon and energy source. These are
accumulated in the cytoplasm of cells as granules under conditions of nutrient imbalance. Accumulation usually occurs when carbon is in excess and if atleast one other nutrient, which is essential for growth, is depleted.
These polyesters are used in a number of applications and have attracted considerable industrial attention. Hence these polymers are gaining attention as alternatives to synthetic plastics. PHA being thermoplastic polyester has the potential to replace petrochemical plastics in a majority of applications. The extensive range of physical properties and broadened performance obtained by compounding and blending is exploited in such applications. Various applications for PHAs have been envisaged which includes molded containers, backsheet of hygiene articles such as diapers, coating agents, packaging materials etc. It is exploited in bulk applications such as coatings, low strength packing, medium strength structural materials, medical temporary implants (such as scaffolding for
the regeneration of arteries and nerve axons), water based latex paints etc. A wide variety of bacteria both gram positive and gram negative, aerobic,anaerobic, photosynthetic, lithotrophs and organotrophs are known to
accumulate PHA intracellularly as carbon and energy source. Even though numerous bacteria are known to produce PHA during their growth, only a few are
reported to produce high concentrations of PHA in their biomass. These organisms have limitations and hence the potential of other microorganisms in this regard needs to be explored. There is a lot of diversity among bacteria with
regard to quantity and quality of PHA accumulated. Because of this diversity there is scope to discover better producers. Hence there is a need to explore indigenous bacterial cultures for PHA accumulating capability. The members of the family Rhizobiaceae differ in the mode of adaptations to stress and imbalanced nutrient conditions. They offer a variety of metabolic pathways directing carbon towards synthesis of biopolymers such as polysaccharides or
polyhydroxyalkanoates. It is therefore interesting to study the intricacies of carbon metabolic traffic being directed either towards polyhydroxyalkanoate synthesis or polysaccharide biosynthesis with respect to Rhizobia.
This study aims at studying the capability of a locally isolated bacterium, Rhizobium meliloti 14 for high production of biopolymer such as polyhydroxyalkanoates. This is an effort towards development of natural plastics from bacteria, which have potential to replace synthetic plastics and thereby in the long run eliminate the non-degradable plastics.