Olive oil mill wastewater valorisation by fungi

Abstract

This paper presents a brief survey of studies conducted at the Laboratory of Applied and Environmental Microbiology of the University of Tuscia on the possible biotechnological valorisation of olive mill wastewater (OMW) using fungi. Besides being a serious environmental problem, OMW might be a possible resource owing to the presence of added value products (e.g. antioxidants) and of simple and complex sugars as a basis for fermentation processes. To this end the technical feasibility of various fungal fermentative processes either to obtain products of high added value or to improve its agronomic use has been assessed. With regard to the former aspect the following cases of study are described: production of enzymes, such as lipase by Candida cylindracea NRRL Y-17506, laccase and Mn-dependent peroxidase by Panus tigrinus CBS 577.79 and pectinases by Cryptococcus albidus var. albidus IMAT 4735, and exopolysaccharide production by Botryosphaeria rhodina DABAC-P82. As far as agronomic use of the waste is concerned, a process based on the acidogenic fungus Aspergillus niger NB2 and aimed at increasing the phosphorus content of OMW is also reported.

Fed‐batch fermentation of olive mill wastewaters for lipase production

“…Several authors had previously screened some yeast strains and other microorganisms for lipase production and C. cylindracea is often pointed out as the best lipase producer. 7,8 Regarding OMW degradation, other authors reported that COD concentration gradually decreases throughout the experiments, 3,7,19 however in the herein reported batch experiments, negligible COD degradation was obtained. In fact, the OMW used in this study presented an extremely high value of COD (261 g L −1 ) while other authors generally use OMW with COD values below 100 g L −1 .…”

“…In fact, the OMW used in this study presented an extremely high value of COD (261 g L −1 ) while other authors generally use OMW with COD values below 100 g L −1 . 3,7,19,20,21 Although this concentration has not been toxic for the microorganisms, it did not allow COD degradation.…”

Bioremediation and biovalorisation of olive-mill wastes

“…1 Simplified flow chart of industrial-scale olive oil extraction processes: traditional press-cake system, three-phase decanter system and two-phase centrifugation system terms of phenolic compounds is up to a thousand times larger than that of domestic sewage (Niaounakis and Halvadakis 2004). Due to their instability, OMWW phenols tend to polymerise during storage into condensed high-molecular-weight polymers that are particularly difficult to degrade (Ayed et al 2005;Crognale et al 2006). For these reasons, the uncontrolled disposal of OMWW has traditionally become a great problem in Mediterranean countries because of their polluting effects on soil and water (Sierra et al 2001;Piotrowska et al 2006).…”

“…The production of enzymes by fungi using OMWs as substrate with commercial interest offers another interesting opportunity for the biotechnological valorisation of the residues. The microbial enzymes obtained by fungal treatment of OMWs include different families of lipases, laccases, Mn-dependent peroxidases and pectinases (Crognale et al 2006).…”

“…Amongst a series of fungal strains belonging to the known lipolytic species, D'Annibale et al (2006) found a promising potential for lipase production by Candida cylindracea NRRL Y-17506. The aromatic-degrading ability of white rot fungi is associated with the production of extracellular oxidases, enzymes with low substrate specificity and good stability against various potentially denaturing agents and thus with a possible use in a wide range of industrial applications (Crognale et al 2006). Within this context, the production of laccases and Mn-dependent peroxidases by OMWW fermentation by Panus tigrinus CBS 577.79, a strain able to cope with high organic loads, has been proposed (D'Annibale et al 2004b).…”