Solid-state cultivation of fungal strains P79 on spent coffee grounds for the extraction of antioxidant phenolic compounds and proteins

Four fungal strains (Aspergillus ustus PSS, Mucor sp. 3P, Penicillium purpurogenum GH2 and Neurospora crassa ATCC10337) were cultivated under solid-state conditions on spent coffee grounds (SCG) aiming to extract antioxidant phenolic compounds and proteins. Cultivations were performed at 30 ºC for 6 days. The produced extracts were characterized regarding the contents of total phenolic compounds, flavonoids, proteins, and antioxidant activity, which was determined by two methods (ferric reducing antioxidant power (FRAP) assay and 1,1-diphenyl-2-picrylhydrazyl (DPPH) method). N. crassa released the highest contents of phenolic compounds (10.99 mg gallic acid equivalents/g SCG) and 0.83 mg protein/g SCG. P. purpurogenum released the highest contents of protein (0.90 mg/g SCG) and flavonoids (0.53 mg quercetin/g SCG) from this raw material. In terms of antioxidant activity, the extract produced by Mucor sp. presented the highest values either by the FRAP (0.047 mM Fe(II)/g SCG) and DPPH (81.9%) methods, and the extract produced by A. ustus also contained elevated antioxidant activity by the DPPH method (81.6%). These results reveal that the studied fungal strains have different ability to degrade SCG, and the selection among them must be done based on the product that is desired to obtain. Solid-state cultivation with fungi was proved to be a useful and environmentally-friendly alternative to extract valuable compounds from SCG

Chemical, functional, and structural properties of spent coffee grounds and coffee silverskin

Spent coffee grounds (SCG) and coffee silverskin (CS) represent a great pollution hazard if discharged into the environment. Taking this fact into account, the purpose of this study was to evaluate the chemical composition, functional properties, and structural characteristics of these agro-industrial residues in order to identify the characteristics that allow their reutilization in industrial processes. According to the results, SCG and CS are both of lignocellulosic nature. Sugars polymerized to their cellulose and hemicellulose fractions correspond to 51.5 and 40.45 % w/w, respectively; however, the hemicellulose sugars and their composition significantly differ from one residue to another. SCG and CS particles differ in terms of morphology and crystallinity, but both materials have very low porosity and similar melting point. In terms of functional properties, SCG and CS present good water and oil holding capacities, emulsion activity and stability, and antioxidant potential, being therefore great candidates for use on food and pharmaceutical fields.The authors acknowledge the financial support of the Science and Technology Foundation of Portugal (FCT) through the grant SFRH/BD/80948/2011 and the Strategic Project PEst-OE/EQB/LA0023/2013. The authors also thank the Project "BioInd - Biotechnology and Bioengineering for improved Industrial and Agro-Food processes", REF. NORTE-07-0124-FEDER-000028 co-funded by the Programa Operacional Regional do Norte (ON.2-O Novo Norte), QREN, FEDER. Thanks are also given to Prof. Jose J.M. Orfao, from the Department of Chemical Engineering, Universidade do Porto (Portugal), for his assistance with the porosity analyses

Production, composition, and application of coffee and its industrial residues

Coffee is one of the most consumed beverages in the world and is the second largest traded commodity after petroleum. Due to the great demand of this product, large amounts of residues are generated in the coffee industry, which are toxic and represent serious environmental problems. Coffee silverskin and spent coffee grounds are the main coffee industry residues, obtained during the beans roasting, and the process to prepare “instant coffee”, respectively. Recently, some attempts have been made to use these residues for energy or value-added compounds production, as strategies to reduce their toxicity levels, while adding value to them. The present article provides an overview regarding coffee and its main industrial residues. In a first part, the composition of beans and their processing, as well as data about the coffee world production and exportation, are presented. In the sequence, the characteristics, chemical composition, and application of the main coffee industry residues are reviewed. Based on these data, it was concluded that coffee may be considered as one of the most valuable primary products in world trade, crucial to the economies and politics of many developing countries since its cultivation, processing, trading, transportation, and marketing provide employment for millions of people. As a consequence of this big market, the reuse of the main coffee industry residues is of large importance from environmental and economical viewpoints

Sugars metabolism and ethanol production by different yeast strains from coffee industry wastes hydrolysates

Significant amounts of wastes are generated by the coffee industry, among of which, coffee silverskin (CS) and spent coffee grounds (SCG) are the most abundantly generated during the beans roasting and instant coffee preparation, respectively. This study evaluated the sugars metabolism and production of ethanol by three different yeast strains (Saccharomyces cerevisiae, Pichia stipitis and Kluyveromyces fragilis) when cultivated in sugar rich hydrolysates produced by acid hydrolysis of CS and SCG. S. cerevisiae provided the best ethanol production from SCG hydrolysate (11.7 g/l, 50.2% efficiency). On the other hand, insignificant (⩽1.0 g/l) ethanol production was obtained from CS hydrolysate, for all the evaluated yeast strains, probably due to the low sugars concentration present in this medium (approx. 22 g/l). It was concluded that it is possible to reuse SCG as raw material for ethanol production, which is of great interest for the production of this biofuel, as well as to add value to this agro-industrial waste. CS hydrolysate, in the way that is produced, was not a suitable fermentation medium for ethanol production; however, the hydrolysate concentration for the sugars content increase previous the use as fermentation medium could be an alternative to overcome this problem

Extraction of value-added compounds from spent coffee grounds using supercritical fluid

In this work, supercritical fluid extraction (SFE) using carbon dioxide (CO2) as solvent was used for the recovery of antioxidant phenolic compounds and proteins from spent coffee grounds (SCG). Extraction assays were carried out under different conditions of temperature and pressure. The highest contents of flavonoids (164.57 mg QE/g extract), protein (160.97 mg BSA/g extract), and antioxidant activity (FRAP = 0.5843 mM Fe (II)/g extract; and total antioxidant capacity = 272.26 mg α-tocopherol/g extract) were obtained when using 250 bar and 333.15k. On the other hand, SFE at 200 bar and 313.15k was the best condition to recover phenolic compounds from SCG (33.63 mg GAE/g extract)

Fungal growth on coffee husks and spent ground under solidstatecultivation conditions

The processing of coffee generates significant amounts of agricultural wastes. Coffee husks, comprised of dry outer skin, pulp and parchment, are probably the major residues from the handling and processing of coffee (1). Coffee spent ground is the main coffee industry residue obtained during the processing of raw coffee powder to prepare instant coffee. Coffee husks and spent ground are generated in more than two millions tons yearly (2), and the major problem encountered by the industries is the disposal of these residues, since they contain some amount of caffeine, polyphenols and tannins, which makes them toxic in nature (3). Filamentous fungi are microorganisms able to growth over complex substrates behind minimal conditions, and play an important role in the generation of natural compounds with high commercial interest. Therefore, the aim of the present work was to evaluate the ability of some fungal strains to growth on coffee husks (basically the parchment skin the hull that surrounds the coffee bean), and spent grounds, as an alternative to add value to these toxic residues. Strains from the genus Aspergillus, Penicillium, Mucor and Neurospora were used. Microbial growth was carried out in Petri plates containing 30% of coffee husks or spent ground and 70% of CzapekDox saline media, pH 5.0. The plates were inoculated with a suspension containing 5´106 spores/g dry residue, and maintained at 28ºC for 5 days. The spore suspension was prepared by scrap down the spores from PDA plates with a sterilized solution of 0.2% Tween 80, and counted in a Neubauer chamber. Cultivations were done in duplicate to each fungal in each different substrate. Radial growth rate (Ur, mm/h) was monitored kinetically measuring colony diameters every 12h. All the evaluated fungal strains showed mycelium presence over both residues. For almost all the strains, the invasion capacity was higher in coffee spent ground than in coffee husks. Highest growth rates were obtained with Neurospora crassa, with values of 0.99 and 0.76 mm/h for spent ground and husks, respectively. It was thus concluded that coffee husks and spent grounds can be successfully used as substrate for fungal strains growth. Among the evaluated strains Neurospora crassa gave the best results and could be thus evaluated in solidstate fermentation processes for the obtainment of compounds with commercial interest from these two agroindustrial residues

Solid-state fermentation: a strategy for biological detoxification of coffee industry residues

Coffee is the second largest traded commodity in the world, after petroleum, and therefore, the coffee industry is responsible for the generation of large amount of residues. Among these residues, coffee silverskin (CS) and spent coffee grounds (SCG) are generated in significant amounts and merit special attention. Despite the large generation, most of these residues are unutilized, being discharged to the environment or burned for elimination, which are not environmentally friendly techniques. The discharge to the environment cause severe contamination and environmental pollution problems due to their toxic nature (presence of polyphenols, caffeine, and tannins), and burning results in the production of carbon dioxide, the green house gas. If the toxic constituents present in these materials could be removed, or, at least degraded to a reasonably low level, it would open new opportunities for the utilization of these residues. Therefore, the development of methods to decrease their toxicity or to utilize them as raw material for the production of value added compounds is of great relevance. Solid-state fermentation (SSF) can be defined as the growth of microorganisms on moistened solid substrate, in which enough moisture is present to maintain microbial growth and metabolism, but there is no free-moving water. In recent years, SSF has received more interest from researchers since several studies have demonstrated that this process may lead to higher yields and productivities or better product characteristics than submerged fermentation systems. Based on the above mentioned aspects, the present study consisted in evaluating the ability of seven different fungal strains from the genus Aspergillus, Mucor, Penicillium, and Neurospora, to grow and release phenolic compounds from CS and SCG under solid-state cultivation conditions, as an alternative for biological detoxification of these residues. The biomass production and content of phenolic compounds released from the substrates were monitored during the cultivations. According to the results, Penicillium purpurogenum, Neurospora crassa and Mucor released the highest amount of phenolic compounds from the materials, contributing thus for their detoxification, since phenolic compounds are closely related to the material toxicity. Biological detoxification of CS and SCG provides environmental benefits for the disposal of these residues, as well as economical benefits for the conversion of them to value added products that can be industrially applied