STRUCTURE AND DYNAMICS OF MICROBIAL COMMUNITIES IN ANAEROBIC DIGESTION PROCESSES

Nowadays world energy needs rely mostly on fossil fuels (oil, coal and natural gas) which accounts for more than 80% of global energy production. Fossil fuels reserves are estimated to deplete in the next future. In this context, it arises the need to establish new renewable energetic sources. A well-established technology for bioenergy production in the form of biogas is anaerobic digestion (AD). This process involves a complex consortium of different functional groups of microbes which, degrading the organic matter, produce biogas composed mainly of methane and carbon dioxide. In the latest 10 years there has been renewed interest for energy production from biomass through AD because of its versatility and potentiality. So far, the control and performance of AD process has typically been performed working on operational parameters (such as T, pH, COD, loading rate, etc.). However, recent studies concerning the microbial consortia involved in this complex process have been developing with the final aim to get an exhaustive knowledge of microbiology of the process and how it correlates to the operation of the reactor in order to improve the digester performance making preventive action possible. the general aim of this PhD thesis was to investigate the microbiology of both batch and continuous, single and two-stage anaerobic systems. The goals were (i) to elucidate the structure of the microbial communities, (ii) to investigate the dynamics, interactions and responses of the key metabolic groups responsible for the degradation of substrates and (iii) to give valuable information on the correlation between structure and function inside the microbial consortiums.