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

The cultivation of mushrooms on wheat straw can be considered a solid state fermentation, yet following harvest the residual, partially degraded straw is discarded. During cultivation, the degradation of lignocellulose in the straw takes place by the fungus under the action of enzymes releasing degradation products with small molecular weight, some of which are potentially valuable. 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. The aqueous extraction releases water soluble compounds, such as sugars and phenolics with lower molecular weight, which are easily obtained. The partially degraded straw may then be treated with organic solvents to release water insoluble lignin breakdown products, such as fatty acids, phenolics and other aromatics. It is important to conduct scale-up 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 (20oC, 25oC, 40oC, 60oC and 80oC) and water-to-dry straw ratio (from 40:1 to 90:1) on the total extracted matter and especially on sugar and phenolic compounds yields. A microbial study of the aqueous extract was also performed at 20oC and 25oC to explain the high concentration of organic carbon in the extract under certain circumstances. The optimum extraction conditions were determined by taking into account the yield and the energy consumption of the process. The conclusion was that the extraction temperature can be conducted between 20oC and 25oC with good results for obtaining liquor which can be used in a biogas installation. The extraction should be conducted at 80oC to obtain greater yields of sugars and phenolics

Liquid-liquid extraction with and without a chemical reaction

The extraction of mercaptans with alkaline solution is accompanied by a second- order instantaneous reaction. As explained in Section 2.2, in this case, the mass transfer coefficients can be calculated as for the physical extraction, since the mass transfer is much slower than the reaction rate.The liquid-liquid extraction is a mass transfer process between two phases. One liquid phase is the feed consisting of a solute and a carrier. The other phase is the solvent. The extraction is understood to be a transfer of the solute from the feed to the solvent. During and at the end of the extraction process, the feed deprived of solute becomes a raffinate and the solvent turns into extract. Extraction is a separation process aiming to purify the feed or to recover one or more compounds from it

Heat and mass transfer study during wheat straw solid substrate fermentation with P.ostreatus

The solid state (substrate) fermentation of the wheat straw with Pleurotus ostreatus is a complex process implying biological, chemical and physical phenomena linked to the fungus growth and the degradation of the straw. Heat and mass transfer during the removal of the metabolic heat and products is an interesting aspect for scaling up to highcapacity facilities. Accurate heat and mass balances help to forecast the utilities needed in the fermentation rooms. In this work, a heat and mass transfer study was worked out for this agro-industrial process at a larger scale than the standard growth of P.ostreatus in small plastic bags and trays. The study consisted on performing heat transfer and mass (water) transfer balances, finding the accurate description of the transfer mechanisms and calculating the transfer coefficients. The practical goal of the study was to measure the metabolic heat and the water vapour adsorbed from air, in order to design the cooling and venting utilities for the fermentation room, as well as the external spraying need

A membrane screening for the separation/concentration of dilignols and trilignols from solvent extracts

Recovery of dilignols–trilignols fraction was studied in this work. Solvent resistant ultrafiltration and nanofiltration membranes were used to fractionate ethanol and ethanol/dichloromethane extracts obtained from straw degraded by Pleurotus ostreatus. It was shown that ultrafiltration is very effective in removing solid suspensions. Permeates from ultrafiltration were processed by nanofiltration membranes with MWCO = 1000, 350, 250, and 200 Da, in a screening study aimed to find the best option for the separation and concentration of the dilignols–trilignols fraction. It was demonstrated that it is possible to separate and concentrate the lignin degradation products with molecular mass of 200–390 Da in an integrated UF/NF process with good yields (60–85%) and concentrating the product tenfold

Extracting valuable compounds from straw degraded by Pleurotus ostreatus

This work aims to the recovery of lignocellulosic waste in an environmentally friendly process, as an alternative to the energy- intensive technologies: steam explosion, subcritical and/or supercritical water treatment, gasification through pyrolisis, etc. A study was made to optimize the extraction conditions of potentially valuable compounds in straw degraded by the fungus Pleurotus ostreatus. The effects of solvent nature, temperature and extraction time were quantified by material balances with a special view to the extracts obtained. Confirmation of the effectiveness of the operations was done by spectrophotometric, HPLC and LC-MS analyses. Following this study, a technology localized to the farm was conceived, requiring few craftsmanship and no special utilities, to obtain a semi-product for further processing. A centralized technology could be also taken into account to process the straw by direct extraction with hot solvents, in order to obtain products yields three times higher than in the case of the aqueous extraction followed by solvent extraction at 20oC

Wealth out of waste

Emerging legislation and increasing social and political demand for more ethical and sustainable manufacturing routes has led researchers to investigate alterations to methods used to produce everyday items. Addressing this problem requires a multi-disciplinary approach to enable a variety of novel technologies. Conventional biorefineries use traditional fermentation to convert biomass to feedstocks such as bioethanol, however there is an untapped resource for sustainable materials being wasted. Straw is made up of three main constituents: cellulose, hemi-cellulose and lignin. Whilst the first two can be readily converted to bioethanol, lignin remains under-exploited. The chemicals structure of lignin has been shown to yield many interesting breakdown products potentially useful on an industrial scale. The use of straw is advantageous due to the surplus currently produced in the U.K. The overriding objective of this program is to develop novel materials from plant waste by utilizing natural mechanisms in a truly innovative solid-state biorefinery. Bacterial and fungal species have been shown to target ligno-cellulosic breakdown followed by extractions to produce metabolic profiles of available chemicals. The chemicals are then able to be converted to or utilized as useful materials such as nutraceuticals, polymers and other high value products. This program is developing underpinning science and technology that can be applied at a local level, but on a global scale, allowing the utilization of local resource to produce sustainable high value products