Use of Different Extracts of Coffee Pulp for the Production of Bioethanol

Utilization of the sugar fraction from Arabica coffee pulp as a carbon source for bacteria producing cellulose and cytotoxicity with human keratinocyte

Coffee pulp (CP), a by-product of coffee production, is an underutilized resource with significant potential value. CP contains monosaccharides that can serve as an ideal carbon source for bacterial cultivation, enabling the production of value-added components such as medical-grade cellulose. Herein, we extracted the sugar fraction from Arabica CP and used it as a supplement in a growing media of a bacteria cellulose (BC), Komagataeibacter nataicola. The BC was then characterized and tested for cytotoxicity. The CP sugar fraction yielded approximately 7% (w/w) and contained glucose at 4.52 mg/g extract and fructose at 7.34 mg/g extract. Supplementing the sugar fraction at different concentrations (0.1, 0.3, 0.5, 0.7, and 1 g/10 mL) in sterilized glucose yeast extract broth, the highest yield of cellulose (0.0020 g) occurred at 0.3 g/10 mL. It possessed similar physicochemical attributes to the BC using glucose, with some notable improvements in fine structure and arrangement of the functional groups. In cytotoxicity assessments on HaCaT keratinocyte cells, bacterial cellulose concentrations of 2-1000 µg/mL exhibited viability of ≥ 80%. However, higher concentrations were toxic. This research innovatively uses coffee pulp for bacterial cellulose, aligning with the principles of a bio-circular economy that focuses on sustainable biomass utilization.

Fractionation and characterization of cell wall polysaccharides from coffee (Coffea arabica L.) pulp

Cell wall polysaccharides were isolated by sequential extractions from coffee pulp, the main solid waste from coffee processing. Extractions were conducted with distilled water at room and boiling temperatures, 0.5 % ammonium oxalate and 0.05 M Na2CO3 to obtain pectic fractions. Hemicelluloses were extracted by using 2 M and 4 M NaOH. The composition of the hemicellulose fractions suggested the presence of xyloglucans, galactomannans and arabinogalactan-proteins (AGPs). The main part of the cell wall polysaccharides recovered from coffee pulp were pectins branched with arabinogalactans. Coffee pulp pectic fractions were low-methoxylated with various amounts of protein (0.5-8.4 %) and phenolics (0.7-8.5 %). Detection at 280 nm in the HPSEC analyses and radial gel diffusion assay using Yariv reagent indicated the presence of AGPs in most of these fractions. NMR analyses of chelating agent (CSP) and dialyzed water (WSPD) extracted pectins were carried out. The results demonstrated that CSP contains only AG I. On the other hand, AG I and AG II are present in WSPD, probably covalently linked to the pectic portion. Comparison with the literature indicated similarities between the cell wall polysaccharides from coffee pulp and green coffee beans.

Value-Added Products from Coffee Waste: A Review

Coffee waste is often viewed as a problem, but it can be converted into value-added products if managed with clean technologies and long-term waste management strategies. Several compounds, including lipids, lignin, cellulose and hemicelluloses, tannins, antioxidants, caffeine, polyphenols, carotenoids, flavonoids, and biofuel can be extracted or produced through recycling, recovery, or energy valorization. In this review, we will discuss the potential uses of by-products generated from the waste derived from coffee production, including coffee leaves and flowers from cultivation; coffee pulps, husks, and silverskin from coffee processing; and spent coffee grounds (SCGs) from post-consumption. The full utilization of these coffee by-products can be achieved by establishing suitable infrastructure and building networks between scientists, business organizations, and policymakers, thus reducing the economic and environmental burdens of coffee processing in a sustainable manner.

Production of Coffee Cherry Spirits from Coffea arabica Varieties

Coffee pulp, obtained from wet coffee processing, is the major by-product accumulating in the coffee producing countries. One of the many approaches valorising this underestimated agricultural residue is the production of distillates. This research project deals with the production of spirits from coffee pulp using three different Coffea arabica varieties as a substrate. Coffee pulp was fermented for 72 h with a selected yeast strain (Saccharomyces cerevisiae L.), acid, pectin lyase, and water. Several parameters, such as temperature, pH, sugar concentration and alcoholic strength were measured to monitor the fermentation process. Subsequently, the alcoholic mashes were double distilled with stainless steel pot stills and a sensory evaluation of the products was conducted. Furthermore, the chemical composition of fermented mashes and produced distillates were evaluated. It showed that elevated methanol concentrations (>1.3 g/L) were present in mashes and products of all three varieties. The sensory evaluation found the major aroma descriptor for the coffee pulp spirits as being stone fruit. The fermentation and distillation experiments revealed that coffee pulp can be successfully used as a raw material for the production of fruit spirits. However, the spirit quality and its flavour characteristics can be improved with optimised process parameters and distillation equipment.

Coffee and Yeasts: From Flavor to Biotechnology

Coffee is one of the most consumed beverages in the world, and its popularity has prompted the necessity to constantly increase the variety and improve the characteristics of coffee as a general commodity. The popularity of coffee as a staple drink has also brought undesired side effects, since coffee production, processing and consumption are all accompanied by impressive quantities of coffee-related wastes which can be a threat to the environment. In this review, we integrated the main studies on fermentative yeasts used in coffee-related industries with emphasis on two different directions: (1) the role of yeast strains in the postharvest processing of coffee, the possibilities to use them as starting cultures for controlled fermentation and their impact on the sensorial quality of processed coffee, and (2) the potential to use yeasts to capitalize on coffee wastes—especially spent coffee grounds—in the form of eco-friendly biomass, biofuel or fine chemical production.

Chemical composition and health properties of coffee and coffee by-products

Coffee can be an ally in the fight against diseases such as type 2 diabetes, cancer, hepatic injury, cirrhosis, depression, suicidal behavior, and neurological and cardiovascular disorders. The properties of coffee also favor gastrointestinal tract and gut microbiota establishment. Coffee bioactive components include phenolic compounds (chlorogenic acids, cafestol and kahweol), alkaloids (caffeine and trigonelin), diterpenes (cafestol and kahweol) and other secondary metabolites. The image of coffee as a super functional food has helped to increase coffee consumption across the globe. This chapter addresses the main health promotion mechanisms associated with coffee consumption. Related topics on coffee production chain, world consumption and reuse of coffee by-products in the production of high-value-adding molecules with potential applications in the food industry are addressed and discussed.

Hydrogen production from coffee pulp by dark fermentation

Coffee pulp (C.P.) is a waste of coffee production that needs to be controlled. Due to its high moisture and sugar content, a diagnostic study that characterizes the pulp was conducted and the potential for hydrogen production was evaluated. Subsequently, the kinetics of hydrogen production in a bioreactor were evaluated. A biodegradability index of 0.91 (DBO₅/DQO) was calculated, initial pH of the sample was 4.16 ± 0.05, a concentration of total volatile solids (TVS) of 58.1 ± 0.94 [g/L], and total sugar of 19.6 ± 0.79 [g Dextrose/L]. The yield was at 49.2 [NmL H₂/g DQO_Initial], the hydrogen production per fresh coffee pulp kilogram was 4.18 [L H₂/kg C.P.], the energy density was determined at 0.045 [MJ/kg C.P.]. Modified Gompertz parameters were 585 [NmL] for H_max, 4.1 [NmL H₂/g DQO-h] for R_max and a lag phase (λ) of 92.70 [h]. Because the yield of hydrogen production of coffee pulp estimated was similar to complex substrates like tequila vinasses, and there was a DQO reduction of 13.58%, based on some substrate restrictions, dark fermentation could be a stage of pretreatment of wastewater with coffee pulp in a biogas process to produce two relevant economic and energy products (hydrogen and biogas).

Effects of coffee processing residues on anaerobic microorganisms and corresponding digestion performance

The objective of this study was to delineate the effects of different coffee processing residues on the anaerobic microbes and corresponding digestion performance. The results elucidated that mucilage-rich feed enhanced the accumulation of methanogens, which consequently led to better digestion performance of biogas production. Fifty percent more methane and up to 3 times more net energy (heat and electricity) output were achieved by the digestion of the mucilage-rich feed (M3). The microbial community and statistical analyses further elucidated that different residues in the feed had significant impact on microbial distribution and correspondingly influenced the digestion performance.

A comprehensive review on utilization of wastewater from coffee processing

The coffee processing industry is one of the major agro-based industries contributing significantly in international and national growth. Coffee fruits are processed by two methods, wet and dry process. In wet processing, coffee fruits generate enormous quantities of high strength wastewater requiring systematic treatment prior to disposal. Different method approach is used to treat the wastewater. Many researchers have attempted to assess the efficiency of batch aeration as posttreatment of coffee processing wastewater from an upflow anaerobic hybrid reactor (UAHR)-continuous and intermittent aeration system. However, wet coffee processing requires a high degree of processing know-how and produces large amounts of effluents which have the potential to damage the environment. Characteristics of wastewater from coffee processing has a biological oxygen demand (BOD) of up to 20,000 mg/l and a chemical oxygen demand (COD) of up to 50,000 mg/l as well as the acidity of pH below 4. In this review paper, various methods are discussed to treat coffee processing wastewaters; the constitution of wastewater is presented and the technical solutions for wastewater treatment are discussed.