Recovering low molecular weight extractives from degraded straw by oyster mushroom at the farm scale for high value use

During the cultivation of mushrooms on straw, the degradation of lignocellulose takes place under the action of enzymes releasing degradation products with small molecular weight, some of which are potentially valuable (sugars, phenolics, fatty acids, etc). These compounds may be extracted from straw after mushroom cultivation in two stages: an aqueous extraction followed by a solvent extraction. The present work is focused on the first stage of the process where water soluble compounds are extracted. It is important to conduct experiments at a scale that would reflect the amount of waste straw generated by a mushroom farm. A study was performed using a vessel of 300 L capacity with mixing impeller, by observing the influence of the temperature, extraction time and water-to-dry straw ratio on the total extracted matter and especially on sugar and phenolic compounds yields. The optimum extraction conditions were determined by taking into account the yields. From this study, it emerged that the room temperature is recommended, the water-to-straw ratio would not exceed 40:1 kg kg−1 of dry straw and the extraction time should be limited to 4 h.