Chirke, Sahadev Shrihari

English

Open Access Repository of Indian Theses

		AbstractThe majority of conventional plastics are produced based on fossil fuels. Conventional plastics are durable and degrade slowly and their incineration releases pollutants, they contribute to environmental problems. In response to the world’s growing awareness about environment and limited fossil fuel resources, intensive research have focused on the production of bioplastics as “green” alternatives to synthetic plastics. Bioplastics such as polyhydroxyalkanoates (PHA) have attracted great interest due to their biodegradable nature. PHA are high molecular weight carbonaceous compounds produced as cellular reserve storage products under excess carbon and nutrient deprived conditions to protect bacteria against starvation. PHA has special physical traits, such as the elasticity, high crystallization rate, high degree of polymerization and can be converted to a wide range of finished products for application in industry, agriculture and medicine. One of the major drawbacks for commercialization of PHA production is the high production cost, in which feedstock accounts for 50% of the overall price. Hence, there is a big interest in the use of cheap renewable resources. PHA production from renewable resources and their complete biodegradability make them promising from an environmental point of view. A considerable effort has gone in production of PHA using mixed cultures of microorganisms and cheaply available wastewater. The merits of PHA production with mixed culture include an enhanced economy, a simpler process control, non sterile conditions and an improved use of wastes. Mixed culture utilization can lower the input costs by allowing for large scale fermentations to occur without overhead costs of sterilization. It also allows for a greater variety of substrates to be used due to the presence of several PHA producing organisms. As an alternative to sugars, to attain commercial viability as well as to further improve the sustainability profile of PHA production by fermentation, cheap renewable resources or secondary raw materials must be used instead of expensive carbohydrates such as glucose. Utilization of wastewater as substrate and mixed culture as biocatalyst makes these technologies as sustainable for bioplastics production as well as waste management. Waste/wastewater generally contains good amount of organic matter which can be considered as an ideal commodity to produce bioplastics. Various studies have already been conducted in the direction of utilizing wastewater as substrate, but many other organic waste streams are available as well and are currently not valorized. However, there still remain certain limitations to overcome these technologies to become alternatives for the traditional energy production processes. Lower substrate conversion efficiency, enhancement of bioplastics production, production of co-polymer instead of homopolymer is the major concerns which should be addressed prior to the up scaling of bioplastics production. In this context present thesis deals with some of the strategies to reduce the substrate cost, and regulate microbial metabolism towards enhancement of bioplastics production. Mixed culture bioplastics production process was understood by optimizing different critical factors and PHA production was enhanced using Taguchi – DOE methodology. PHA was produced using different types of pure substrates and waste streams with pure and mixed type of bacteria. PHA production was enhanced by employing bioaugmentation strategy and by addition of co-factor (molybdenum). Bioelectrochemical behavior of biocatalyst during PHA production was evaluated using cyclic voltammetry. Microbial diversity analysis was done for mixed culture to know the organisms involved in PHA production process by using molecular biology techniques. Bioplastics production process was integrated with acidogenic fermentation to utilize the acid rich effluents generated during hydrogen production process towards reduce production cost along with additional waste remediation. 

Divergent and stereoselective approach for the synthesis of some polyhydroxy pyrrolidine, piperidie and pyrrolizidine iminosugars

http://eprints.csirexplorations.com/1048/1/Abstract.doc

Divergent and stereoselective approach for the synthesis of some polyhydroxy pyrrolidine, piperidie and pyrrolizidine iminosugars

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