Objective: To study the growth & biopolymer accumulation kinetics of Wautersia eutropha under batch cultivation conditions in bioreactor.

Theory: Basic concepts & need of biopolymer production

Synthetic polymers have become an essential part of our life due to their properties of durability, strength, lightness and cost. These very desirable properties have also made the plastics a source of environmental and waste management problem. Also these polymers are primarily derived from non renewable fossil (petrochemical) which are disappearing fast. Ideally the polymer should not only be biodegradable but also be produced from renewable resources. As a solution to this, biodegradable plastics (mainly polyhydroxyalkanoates (PHA)) have been developed through biotechnological routes. These are polyesters of various hydroxyalkanoates which are synthesized by numerous microorganisms as energy reserve materials when an essential nutrient such as nitrogen or phosphorus is limited in presence of excess carbon source. They are also completely degraded to water and carbon dioxide under aerobic conditions and to methane under anaerobic conditions by microorganisms in soil, sea, lake water and sewage. But the main property which sets them apart from other polymers is their similar mechanical properties to the synthetically produced polymers like polypropylene. They can be used for the development of disposable items, packaging films, and also as biodegradable carriers.

Poly-β-hydroxybutyrate (PHB), the most widespread and best characterized member of PHAs, is a homopolymer consisting of 3-hydroxybutyrate (HB). Organisms producing PHB include a wide variety of taxonomically different groups. Among all, Wautersia eutropha (formerly known as Ralstonia eutropha and Alcaligenes eutrophus) has been most extensively studied due to its ability to accumulate large amount of PHB from inexpensive sources. It features accumulation of biopolymer when there is a limitation of an essential nutrient such as nitrogen, phosphorous, magnesium or sulfur in the presence of excess carbon source. There is a need to understand the kinetics of growth and product formation by Wautersia eutropha under batch cultivation mode so that a mathematical description of the biological process can be established. This model will be highly instrumental in identification of right bioreactor configuration and appropriate cultivation strategy so that the biopolymer concentration and productivity by microbial cultivation can be enhanced.