BIODEGRADATION OF POLYCAPROLACTONE BIOPLASTIC IN COMPARISION WITH OTHER BIOPLASTICS AND ITS IMPACT ON BIOTA

Abstract

The world is facing many global challenges and one of these is the waste disposal management problem, which arose due to the high production of plastics worldwide. Synthetic plastic waste can accumulate in the environment for decades or even centuries due to their recalcitrant nature. As a way of solving this problem, the production and use of biodegradable polymers (BDPs) have been gradually increased. Naturally, biodegradable polymers decompose into carbon dioxide, water, inorganic compounds, methane and biomass via microbial activity. Polyhydroxybutyrate (PHB), polybutylene succinate (PBS), polylactic acid (PLA), and polycaprolactone (PCL) are examples of the available BDPs. PCL is a synthetic, aliphatic polymer that is compatible with other polymers and has many applications. There have been extensive researches on the microbial degradability of many polymers under different conditions. However, in addition to the biodegradability of these BDPs, the biodegradation rate and the suitable environment for the degradation of each polymer need to be evaluated in order to decide the suitable waste management method. Moreover, the impact of the products from the degradation of BDPs on the environment and their effect on biota require more investigations. Therefore the aims of this research was to (a) determine the rate of microbial degradation of four biodegradable polymers in soil and compost under different conditions, (b) to investigate the degradation of PCL in different forms to determine the characterisation of PCL as a promising biodegradable polymer, (c) to determine the impact of PCL degradation on microbial communities in compost at different temperatures using next generation sequencing, and (d) to determine if PCL degradation has any effect on seed germination in compost. The conditions of the burial environment had a clear and direct effect on the degradation of different BDPs. The degradation of PCL was the fastest and temperature was highly correlated to the rate of PCL degradation under controlled conditions. The degrading microorganisms that were isolated from the surface of the polymers were identified and found that Thermomyces lanuginosus was the main PCL degrader at 50°C in compost. When testing the effect of PCL degradation on microbial community structure it was been found that fugal communities were distributed according to the presence of PCL at each temperature. However, temperature as well was a factor for fungal community structure variation overall. Under most conditions PCL has no adverse effect on the germination of seeds. However, PCL with concentration of 5% and above inhibited cress seed germination when incubated at 55°C.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Jon Pittman (Supervisor)