Journal of Life Sciences 9 (2015) 139-151 doi: 10.17265/1934-7391/2015.04.001 Characterization and Enhancement of Microbial Biodiversity in Digestate in the Agronomic Field Giuliana Conversano, Graziano Pizzolante, Pietro Alifano and Luigi De Bellis Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, Università del Salento, Via Prov.le Lecce-Monteroni, Lecce 73100, Italy Received: March 3, 2015 / Accepted: April 18, 2015 / Published: April 30, 2015. Abstract: The possibility of producing biogas and methane from two phases olive pomace was considered using anaerobic digestion and the microbial characteristic of digestate for the agrarian use was analyzed. In the work, the main aim was to obtain biogas, made from at least 50% methane, and a digestate that can be used in the field of agronomy, from the anaerobic digestion of the substrates. The tests were carried out by digesting different mixtures of the two-phase pomace, mulberry leaves and mud civil wastewater (pre-digested) in a batch system and in anaerobic mesophilic conditions (35 °C). The substrates were properly homogenized in order to obtain mixtures of known and uniform composition. The initial and final STi (Total Solids) and initial SVi (Volatile Solids), the concentration of chemical oxygen demand and total phenols were measured and the process yield (m3/t SV) was quantified with standard procedure. The objectives of the study were the analysis of microbial biodiversity developed during fermentation of mixtures based products and the microbial communities corresponding to Eubacteria, Archaea and Fungiwas analyzed. The suitability of the digestate for agronomical use was evaluated by estimating pathogens bacteria that may be present and by index of inhibition of plant organisms model. Key words: Olive pomace, anaerobic digestion, Methane, digestate, microbial community. 1. Introduction Following the energy crisis of the 70s concerns about the availability of renewable energy sources, considered alternatives to traditional fossil sources have increased. To limit CO 2 emissions and combat climate change, industrialized countries have initiated innovative energy plans [1]. New renewable sources were investigated and biochemical processes were developed. Many sources, such as crops, grasses, leaves, manure, fruit, and vegetables waste have been used and the process has been applied in small and large scales [2]. Anaerobic decomposition of organic compounds is conducted in close cooperation with specialized microorganisms of different type, including mostly hydrolyzing, acidifying, acetogenic, and Correspondigauthor: Giuliana Conversano, Ph.D., research fields: ecology and climate changes. E-mail: giuliana.conversano@unisalento.it. methanogenic one. The final stage of the digestion process produces biogas, containing CO 2 and CH 4 [3]. Anaerobic digestion of energy crops, residues and wastes is of increasing interest in order to reduce the greenhouse gas emissions and to facilitate a sustainable development of energy supply. The success of the biogas production will come from its availability at low costs and the broad variety of usable forms of biogas for the production of heat, steam, electricity and digestate for agronomic use [2]. Salento as Puglia is an area with a high production of olive oil. The choice of subjecting olive pomace to the anaerobic fermentation, is a compromise between the need to dispose of a by-product of difficult management downstream, and concomitant production of biogas rich in methane and convertible into electricity and heat [4]. But the amount of phenols that characterizes the two-phase pomace is significantly greater and it can lead to low yields of D DAVID PUBLISHING