Brewer's spent grain : a valuable feedstock for industrial applications

Brewer's spent grain (BSG) is the most abundant by-product generated from the beer-brewing process, representing approximately 85% of the total by-products obtained. This material is basically constituted by the barley grain husks obtained as solid residue after the wort production. Since BSG is rich in sugars and proteins, the main and quickest alternative for elimination of this industrial by-product has been as animal feed. However, BSG is a raw material of interest for application in different areas because of its low cost, large availability throughout the year and valuable chemical composition. In the last decade, many efforts have been directed towards the reuse of BSG, taking into account the incentive that has been given to recycle the wastes and by-products generated by industrial activities. Currently, many interesting and advantageous methods for application of BSG in foods, in energy production and in chemical and biotechnological processes have been reported. The present study presents and discusses the most recent perspectives for BSG application in such areas. © 2013 Society of Chemical Industry

Lignocellulosic biomass utilization toward biorefinery: technologies, products and perspectives

Lignocellulosic biomass wastes (LBW) are generated and accumulated in large amounts around the world every year. The disposal of large amounts of such wastes in the nature may cause environmental problems, affecting the quality of the soil, lakes and rivers. In order to avoid these problems, efforts have been directed to use LBW in a biorefinery to maximize the reutilization of these wastes with minimal or none production of residual matter. Through biorefinery, the biomass is submitted to different conversion processes that may include biological, physical and chemical technologies to produce fuels, power, heat, food, feed, and valueadded chemicals. The products that can be obtained as well as the technologies that can be used for biomass disruption and conversion vary according to the characteristics of the LBW, such as the physical properties and chemical composition in terms of cellulose, hemicellulose, lignin and protein contents [1]. By producing multiple products through a biorefinery, the value of the biomass feedstock is maximized, which can be of particular interest in countries with abundance of these wastes and also in the underdeveloped countries that can explore better their resources and waste materials. In the future, a significant increase in the implementation of biorefi- nery processes for biomass valorisation is expected motivated by the desire in reducing the impact and toxicity of these wastes to the environment and at the same time to produce compounds of industrial interest from competitive technologies based on the use of low-cost raw materials. The creation of more jobs is another positive and important aspect related to the implementation of these processes on industrial scale

Isolation of polyphenols from spent coffee grounds and silverskin by mild hydrothermal pretreatment

In the present study, a new method for isolation of polyphenols (PP) from spent coffee grounds (SCG) and coffee silverskin (CS) is described. The method consisted in a mild hydrothermal pretreatment at 120 °C, during 20 min, using a liquid to solid ratio of 20 ml/g. PP (determined as gallic acid equivalents, GAE) were the most abundant components in the extracts produced by this method, corresponding to 32.92 mgGAE/gSCG and 19.17 mgGAE/gCS, among of which, flavonoids corresponded to 8.29 and 2.73 mg quercetin equivalents/g of SCG and CS, respectively. Both extracts presented antioxidant activity but the results were higher for SCG extract, probably due to the highest content of PP present. Negligible effects (less than 1% solubilisation) were caused by the hydrothermal pretreatment on cellulose, hemicellulose and protein fractions of these materials. Some minerals elements were present in the extracts, potassium being the most abundant. Hydrothermal pretreatment under mild conditions was demonstrated to be an efficient method to recover antioxidant PP from coffee residues

Hydrothermal pretreatment of spent coffee and silverskin for polyphenols recovery

Coffee is one of the most consumed beverages around the world. As a consequence of this big market, huge amounts of residues are also generated every year as a result of the coffee beans processing. Spent coffee grounds (SCG, Figure 1a), for example, are obtained in significant amounts during the process for instant coffee elaboration, and is also obtained in large amounts in restaurants, bars and cafeterias; while coffee silverskin (CS, Figure 1b) is the main residue obtained during the beans roasting step [1]. Interest in reusing these residues has increased in the last years for economic and environmental concerns. Additionally, such coffee wastes contain in their composition several compounds of interest for application in food, cosmetic and pharmaceutical areas [1]. The presence of polyphenols (PP) in SCG and CS has been reported in several studies, and some technologies have also been proposed for the recovery of these compounds from such coffee residues, among of which the use of organic solvents is usually proposed due to their efficient extraction capacity. However, the use of organic solvents generates a toxic effluent that needs to be treated before discharging to the environment. As an alternative to avoid this problem, the present study evaluated the possibility of recovering PP by hydrothermal pretreatment of SCG and CS. By using this strategy, the residues are submitted to a reaction using only water as extraction solvent under higher temperature conditions than those usually employed for extraction with organic solvents, and the use of these toxic chemicals is avoided. The hydrothermal pretreatment of SCG and CS consisted in using 20 mL of distilled water to each gram of residue, and the reactions were maintained at 120 ºC during 20 min. The total amount of PP in the extracts was quantified as gallic acid equivalents (GAE). The extracts produced under these conditions contained 32.9 mg GAE/g SCG and 19.2 mg GAE/g CS, among of which, flavonoids corresponded to 25% and 14% of the total PP in SCG and CS, respectively. These results were higher than the amounts recovered in previous studies using organic solvents (methanol and ethanol) as extraction agent [2, 3]. It was then concluded that is possible to use a hydrothermal pretreatment to efficiently recover PP from coffee wastes. Further studies will be focused on the selection of the extraction conditions that maximize the recovery results

Lignocellulose as raw material in fermentation processes

Lignocellulose in the form of forestry, agricultural, and agro-industrial wastes is accumulated in large quantities every year. These materials are mainly composed of three groups of polymers, namely cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are sugar rich fractions of interest for use in fermentation processes, since microorganisms may use the sugars for growth and production of value added compounds such as ethanol, food additives, organic acids, enzymes, and others. Submerged and solid-state fermentation systems have been used to produce compounds of industrial interest from lignocellulose, as an alternative for valorization of these wastes and also to solve environmental problems caused by their disposal. When submerged fermentation systems are used, a previous stage of hydrolysis for separation of the lignocellulose constituents is required. This work is an overview about the potential uses of lignocellulosic materials in fermentation processes. Aspects related to submerged and solid-state fermentation systems will be described focusing on the raw materials, hydrolysis processes, fermentation conditions, microorganisms, and products that can be obtained

Solid-state fermentation as a strategy to improve the bioactive compounds recovery from Larrea tridentata leaves

Chemical composition of Larrea tridentata leaves was determined and elevated content of lignin (35.96 % w/w) was found. The present study was proposed in order to evaluate the extraction of bioactive compounds, particularly phenolic compounds, by solid-state fermentation (SSF) of L. tridentata leaves. The basidiomycete Phanerochaete chrysosporium was used in the experiments due to its ability to degrade lignin. The concentration of total phenolic compounds in the extracts produced by SSF was determined. Additionally, the extracts were characterized regarding the concentration of flavonoids, quercetin, kaempferol, and nordihydroguaiaretic acid and antioxidant activity. SSF was not an efficient process to recover phenolic compounds from L. tridentata leaves. However, this process was very efficient when used as a pretreatment before the plant extraction with organic solvent (methanol). By submitting the plant to SSF and subsequently to extraction with 90 % (v/v) methanol, the recovery of phenolic compounds was improved by 33 % when compared to the results obtained by methanolic extraction of the non-fermented plant. Scanning electron microscopy micrographs revealed a major disorganization and porosity of the plant structure after fermentation, and Fourier transform infrared spectroscopy spectra indicated a possible solubilization of some constituents of lignocellulose fraction after this process, which may have favored the solvent action in the later stage.This work was supported by FCT (contract/grant numbers: SFRH/BD/40439/2007 and SFRH/BPD/38212/2007)