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BioMed Research International
Volume 2013 (2013), Article ID 546830, 13 pages
http://dx.doi.org/10.1155/2013/546830
Research Article

Composted versus Raw Olive Mill Waste as Substrates for the Production of Medicinal Mushrooms: An Assessment of Selected Cultivation and Quality Parameters

1Agricultural University of Athens, Laboratory of General and Agricultural Microbiology, Iera Odos 75, 11855 Athens, Greece
2Hellenic Agricultural Organization-Demeter, Institute of Kalamata, Lakonikis 85, 24100 Kalamata, Greece

Received 4 April 2013; Accepted 3 July 2013

Academic Editor: Nuri Azbar

Copyright © 2013 Georgios I. Zervakis et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Two-phase olive mill waste (TPOMW, “alperujo”) is a highly biotoxic sludge-like effluent of the olive-oil milling process with a huge seasonal production. One of the treatment approaches that has so far received little attention is the use of TPOMW as substrate for the cultivation of edible mushrooms. Fifteen fungal strains belonging to five species (Basidiomycota), that is, Agrocybe cylindracea, Pleurotus cystidiosus, P. eryngii, P. ostreatus, and P. pulmonarius, were evaluated for their efficacy to colonize media composed of TPOMW, which was used either raw or composted in mixtures with wheat straw in various ratios. Qualified strains exhibited high values of biological efficiency (e.g., 120–135% for Pleurotus spp. and 125% for A. cylindracea) and productivity in subsequent cultivation experiments on substrates supplemented with 20–40% composted TPOMW or 20% raw TPOMW. Only when supplementation exceeded 60% for raw TPOMW, a negative impact was noted on mushroom yields which could be attributed to the effluent's toxicity (otherwise alleviated in the respective composted TPOMW medium). Earliness and mushroom size as well as quality parameters such as total phenolic content and antioxidant activity did not demonstrate significant differences versus the control wheat-straw substrate. The substrates hemicellulose content was negatively correlated with mycelium growth rates and yields and positively with earliness; in addition, cellulose: lignin ratio presented a positive correlation with mycelium growth and mushroom weight for A. cylindracea and with earliness for all species examined. TPOMW-based media revealed a great potential for the substitution of traditional cultivation substrates by valorizing environmentally hazardous agricultural waste.