Short communicationRecovering low molecular weight extractives from degraded straw by oyster mushroom at the farm scale for high value use
Highlights
► Degraded straw after the cultivation of the oyster mushroom exploited to recover valuable products. ► Aqueous extraction performed at the farm on a scale relevant to the mushroom cultivation industry. ► The water-to-straw ratio should be kept as low as possible. ► The extraction time should be limited to 4 h. ► The optimum temperature for the extraction is the room temperature.
Introduction
The mushroom cultivation industry employs naturally occurring lignocellulose-degrading fungi in a solid state fermentation at ambient temperatures [1], [2] to convert straw into high value products, e.g. the oyster mushroom Pleurotus ostreatus [3] or the button mushroom Agaricus bisporus [4]. An integrated biorefinery model may be applied not only to produce mushrooms, but also to extract useful compounds from the residual degraded straw, e.g. C5 and C6 sugars and phenolics for biofuel production, pharmaceutical use, etc. We aim to develop a two stage extraction process to separate these compounds: an aqueous extraction followed by a solvent extraction, under mild conditions. This process can potentially be performed locally, at farm scale. In a previous work [5], the optimum conditions of the extraction process were determined at the laboratory scale. However, it is essential to develop the optimum process at real scale, i.e. a mushroom farm dealing with the disposal of tones of straw.
The present work is focused on the first stage of the process, the aqueous extraction. A study was performed using a vessel of 300 L capacity with mixing impeller, where the influence of the temperature, processing time and water-to-dry straw ratio were assessed for the extraction of total extracted matter and especially sugar and phenolic compound yields. Optimum extraction conditions in terms of product release were identified.
Section snippets
Raw material
The raw material for the study consisted of wheat straw degraded by fungus Pleurotus ostreatus grown in approx 20 kg batch in plastic bags under standard cultivation conditions at the WHRI, University of Warwick, Bioconversion Unit. Briefly, straw was pasteurized for two days in the pasteurization tunnel at 70 °C and atmospheric pressure (using steam from a boiler at 0.3 MPa and 140 °C), then inoculated with P. ostreatus (strain HK35) at a rate of 1.5 kg grain spawn to 100 kg straw, the fungus
Results and discussion
The total matter extracted, the organic carbon and the quantities of sugars and phenols recovered were measured and compared in different extraction conditions.
Conclusions
This study aimed to consider whether the partially degraded straw remaining following the cultivation of the oyster mushroom, P. ostreatus, could be exploited to release lignocellulose breakdown products on a scale relevant to the mushroom cultivation industry.
The aqueous extracts obtained in this process may have potential application in the production of biogas, due to the high content of organic carbon.
In this study a vessel of 300 L capacity was used, reflecting the scale of the process
References (8)
- et al.
Modification of wheat straw lignin by solid state fermentation with white-rot fungi
Bioresour Technol
(2009) - et al.
Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent
Methods Enzymol
(1999) - et al.
Chemical transformation of wheat straw constituents after solid-state fermentation with selected lignocellulose-degrading fungi
Biomass Bioenergy
(1990) - et al.
An integrated approach to utilization of agro-residues through Pleurotus cultivation
Crit Rev Biotechnol
(1987)
Cited by (1)
A membrane screening for the separation/concentration of dilignols and trilignols from solvent extracts
2012, Separation and Purification TechnologyCitation Excerpt :The extracts were obtained by contacting at room temperature for 24 h the solvent with the straw degraded by Pleurotus ostreatus (the oyster mushroom). The authors of the present work described the growth of the mushroom on wheat straw in [27]. The solvent extraction can be preceded by an aqueous extraction.