Coffee Husk Research Articles

Organic arabic coffee husk: Antioxidant and cytoprotective properties and potential impacts on selected human intestinal bacterial populations of individuals with diabetes

Coffee husks are the main by-product of the coffee industry and have been traditionally discarded in the environment or used as fertilizers. However, recent studies have shown that coffee husks have bioactive compounds, such as phenolics and fiber-bound macro antioxidants, offering a range of potential health benefits. This study evaluated the antioxidant capacity, cytoprotective/cytotoxic properties, and stimulatory effects on the relative abundance of selected intestinal bacterial populations of individuals with diabetes of organic coffee husks. Organic coffee husk had good antioxidant capacity, maintained under simulated gastric conditions, with more than 50% of antioxidant capacity remaining. Organic coffee husk exerted cytoprotective properties in Caco-2 cells, indicating that cellular functions were not disturbed, besides not inducing oxidation. Overall, organic coffee husk promoted positive effects on the abundance of distinct intestinal bacterial groups of individuals with diabetes during in vitro colonic fermentation, with a higher relative abundance of Bifidobacterium spp., indicating the availability of components able to reach the colon to be fermented by intestinal microbiota. Organic coffee husk could be a circular material to develop new safe and pesticide-free functional ingredients with antioxidant and potential beneficial effects on human intestinal microbiota.

Hybrid Biopellets Characterization of Gamal Wood (Gliricidia sepium) and Robusta Coffee Husk at Various Compositions

Biopellets from gamal wood (Gliricidia sepium) as a biomass energy resource could be an alternative to replace fossil fuels due to having met standards based on moisture content, ash content, fixed carbon, calorific value, and density. Unfortunately, they still had high levels of volatile matter. Robusta coffee husk was a material with high nitrogen content, which is suspected of being able to bind aromatic substances in volatile organic compounds. This study aims to evaluate the quality of biopellets and determine the optimum composition of the biopellets from gamal wood and coffee husk. The blended composition of gamal wood and coffee husk biopellets studied were 100:0, 75:25, 50:50, 25:75, and 0:100. The biopellets were manufactured using the material size of 40-60 mesh with a pressure of 173.51 MPa. The best biopellet was produced in the composition of 75% gamal wood and 25% coffee husk, with a density of 0.85 g/cm3, moisture content of 8.03%, ash content of 3.92%, volatile substances of 78.01%, fixed carbon of 18.07%, and calorific value of 4,176 cal/g. The biopellet quality met the standards of SNI 8021:2014 and EN 14061-2, except for ash content. Adding coffee husk reduced gamal wood biopellet’s volatile matter, increasing the fixed carbon and density of gamal wood biopellets. Keywords: alkali immersion, bamboo, bio-composite, oriented strand board, pre-treatment

Evaluation of agricultural waste, as a substrate for the artisanal production of the Oyster Mushroom (Pleurotus Ostreatus)

Pleurotus ostreatus is one of the most consumed edible mushrooms worldwide, in Ecuador, there is not much information on the use of agricultural residues that serve as optimal substrates, nor agroclimatic adaptations of the artisanal cultivation of this fungus. The objective of this work was to evaluate different agricultural residues, as a substrate for the artisanal production of the oyster mushroom (Pleurotus ostreatus) in the community of Carmen, Loja, Ecuador. For the development of this work, three treatments with five replicates for each treatment were evaluated, the treatments were evaluated on agricultural residues of: cane bagasse (T1), coffee husk (T2) and rice chaff (T3), the variables that were measured were: earliness, biological efficiency and production rate. The statistical design used was a completely randomized design statistically evaluated by means of an ANOVA with the statistical program R. The results indicated that for the treatment with sugar cane bagasse (T1) the earliness found was between 34 and 44 days, obtaining an average production of 25% and biological efficiency 15%. For the cultivation of the fungus in the coffee husk residues (T2), growth problems were observed; in the treatment with rice chaff (T3) it presented an earliness between 52 and 81 days with an average production rate of 3.2% and an average biological efficiency of 2%. Concluding that cane bagasse is the most recommended agricultural residue for the cultivation of the fungus Pleurotus ostreatus in the community of Carmen, Loja Ecuador.

Iridescent Patterns Production from Solid Film Cellulose Nanocrystals Prepared from Coffee Husks

Iridescent Patterns Production from Solid Film Cellulose Nanocrystals Prepared from Coffee Husks

Employment of Coffee Husk Ash as Proxy with Fine Total & Corn Cob Ash as Cover to Cement for M40 Specific

Employment of Coffee Husk Ash as Proxy with Fine Total & Corn Cob Ash as Cover to Cement for M40 Specific

Integrated characterization of arabica coffee husk tea using flavoromics, targeted screening, and in silico approaches

This study aimed to identify the key volatile compounds in two types of processed arabica coffee husk tea, elucidate their olfactory characteristics, and investigate their antioxidant and anti-inflammatory activities. Sensory evaluation indicated differences between the two groups. A total of 64 and 99 compounds were identified in the C and FC groups, respectively, with 5 identified as key aroma compounds (ROAV≥1). Molecular simulations indicated that four common key aroma compounds were successfully docked with OR1A1 and OR5M3 receptors, forming stable complexes. Furthermore, 14 volatile compounds interacted with 140 targets associated with oxidation and inflammation, linking to 919 gene ontology (GO) terms and 135 kyoto encyclopedia of genes and genomes (KEGG) pathways. Molecular simulations revealed that these volatile components showed antioxidant and anti-inflammatory effects by interacting with core receptors through several forces, including van der Waals, Pi-alkyl, and Pi-cation interactions and hydrogen bonds.

Effect of coffee husk biochar and inorganic NP fertilizer on soil properties, growth and yield of potato (Solanum tuberosum L.) on acidic soil of southwest Ethiopia

Soil acidity and low soil fertility due to nutrient leaching coupled with low inorganic fertilizer usage is a major cause of low crop yields across Southwest Ethiopia. Recently, biochar potential to improve soil fertility has gained significant attention but there are limited studies on the use of biochar in combination with inorganic fertilizers. A field experiment was, therefore, conducted to investigate the effect of combined application of biochar and inorganic NP nutrient on soil physicochemical properties, growth and yield of potato in Andiracha district, Southwestern Ethiopia. The experiment was laid out in randomized complete block design (RCBD) and replicated three times. The treatment consisted of four levels of biochar rates (0, 2.5, 5 and 7.5 t ha−1) and four fertilizer rates of (0, 75,100 and 125% of recommended N P rates). Data were analyzed using SAS version 9.3 Software. Analysis of variance showed that combined application of biochar and inorganic NP fertilizer had highly significant (p < 0.01) effect on days to flowering, stem number, plant height, total leaf area, total dry biomass, marketable tuber number per hill and harvest index and significant (p < 0.05) effect on marketable tuber weight and total tuber weight ha−1. Combined application of 7.5 ton ha−1 biochar with 165 kg N and 60 kg P ha−1 resulted highest tuber yield (42.64 t ha−1), that increased yield by 28.99% compared with recommended NP fertilizer alone (165 kg N ha−1 and 60 kg P ha−1), and by 76.6% compared to the control. The increase was mainly attributed to the improvement in soil physico-chemical properties especially soil pH, CEC, organic matter, total N and available P which is a reflection of increase in soil fertility. Consequently, it was determined that the best course of action for potato production in the area was to apply 7.5 tons of biochar ha−1 together with 165 kg N and 60 kg P ha−1. Therefore, the study recommends adoption of low cost biochar production techniques and capacity building to ensure satisfactory knowledge of biochar use and its adoption by potato growers for soil fertility management and enhanced crop productivity.

Penggunaan Abu Sekam Kopi dan Ordinary Portland Cement terhadap Kuat Tekan Beton Normal

Cement is one of the binders which is commonly used as a concrete-forming material. Currently, there is a lot of coffee husk waste in Takengon, Central Aceh Regency, which contains silica. The basis of using coffee husk ash and OPC cement as an adhesive on the normal compressive strength of concrete. This study aims to determine the influence of using coffee husk ash and OPC cement as an adhesive on the compressive strength of normal concrete at a percentage of 5%, 10% and 15%. The research specimen is cylindrical shape with 15 cm diameter and 30 cm height. The test was carried out at the age of 7 and 28 days by using a compressive strength testing machine. The method of making the specimen is in accordance with the SNI 7656-2012 standard. It is found from the results in the laboratory, coffee husk ash obtains silicate compounds (SiO2) 29.11%, magnesium oxide (MgO) 4.92%, calcium oxide (Cao) 5.33%, ferrioxide (Fe2O3) 4.25% and aluminum oxide (Al2O3). The average compressive strength test results of 7-day old concrete at the percentage of 5% coffee husk ash mixture was 20.21 MPa, at 10% was 20.03 MPa and at 15% was 17,25 MPa. The average compressive strength of concrete at 28 days of age with 5% coffee husk ash mixture is 20.27 MPa at 10% coffee husk ash mixture percentage 19.70 MPa and 15% coffee husk ash mixture 15.46 MPa. Comparison of the results of the compressive strength test for concrete at 7 and 28 days was higher for concrete at 7 days. The results of the different compressive strength tests between the ages of the concrete are caused by the high percentage of coffee husk ash mixture where the higher the coffee husk ash percentage, the weaker the adhesion to the concrete. The percentages of coffee husk ash and OPC cement that meet the design compressive strength of 20 MPa are at 5% and 10% respectively.

A survey of potential and frequency used of local feedstuffs in the concentrate formulations for beef cattle feedlot in Indonesia

Abstract In Indonesia, the most popular system of beef cattle farming is a feedlot system, in which cattle are fattened for 3-6 months before being marketed. For a feedlot system to be successful, the availability of feed throughout the production process is important. Local feedstuff is commonly utilized as concentrate feed for beef cattle. This study aimed to identify the types of local feedstuff, the factors affecting their selection and availability, and the supply chain, particularly in feedlots across Indonesia. The study involved surveys, through questionnaires, interviews, and observation. Farm, feed mill, and supplier of feed visits were made and the management were interviewed regarding the feed commonly used in the farm and feed mills. Descriptive analysis was used to describe the local feedstuff’s availability and potential in the feed supply. The research results show that the local feedstuff most frequently used in sequence were palm kernel meal (11.97%), solid tapioca waste/onggok (9.83%), molasses (8.97%), dried cassava chips (8.55%), coffee husks (7.26%), copra meal (7.26%), bran pollard (6.84%), rice bran (5.13%), rice husks (5.13%), and corn cobs (5.13%). The important factors for selecting the types of feedstuffs used were demand (26.3%) and availability (26.3%). The most important factor impacting the availability of feedstuff was the harvesting season (26%). Feedstuff suppliers consist of four types: producers, distributors, agents, and retailers who fill customer demand, with distributors being the most dominant choice.

Analysis of the Nutritional Quality of Local Feed Ingredients Commonly Used in the Concentrate Formula for Beef Cattle Feedlots in Indonesia

Indonesia's annual beef consumption is experiencing a steady rise. In 2021, the per capita beef consumption amounted to 2.56 kg per person per year, resulting in a total of 696 million kilograms consumed across the country. This quantity is equivalent to the slaughtering of approximately 3.98 million cattle annually. With the increasing growth of the feedlot industry, cattle farmers, including feedlot operators, have the opportunity to enhance the value of agricultural companies in Indonesia by utilizing local feedstuffs. The objective of this study was to assess the suitability and nutritional value of indigenous feed sources for beef cattle in Indonesia. The research utilized feedstuff varieties and characteristics sourced from feedlots spanning since 2012-2021. The employed methodologies encompassed surveys, interviews, and questionnaires. This research involved the collection of both primary and secondary data. The potential and quality of local feedstuff were described using descriptive analysis. This research showed that eight types of local feedstuff could be categorized as energy sources including dehydrated cassava chips with a total digestible nutrients (TDN) value of 84.2% and bran pollard with a TDN value of 66.6%. The fiber sources consisted of corn cob (37.7% crude fiber), coffee husk (38% crude fiber), cocoa bean shell (20% crude fiber), tapioca solid waste/onggok (22% crude fiber), and palm kernel meal (22.1% crude fiber). The protein source consisted of copra meal with a protein content of 22.4%. The physical test most frequently inspected the feed color (18.1%) and odor (18.1%). Moisture examination (24%) was the most frequently used of proximate analysis was employed to identify the chemical composition. In conclusion the existence of eight local ingredients which were categorized into three different types: energy source, protein source, and fiber source commonly used in the concentrate formula for beef cattle feedlots in Indonesia.

Organic amendment composition and sowing depth in coffee Arabica: Effects on seedling growth biometrics

There is a significant production of coffee in the Gedeo zone, southern Ethiopia, which has could generate a huge amount of coffee husk wastes that have polluted the environment. However, organically enriching the soil is an effective method to enhance the development and productivity of coffee. Thus, this study aims to understand the effects of the interaction between sowing depth and organic amending practices. Three sowing depths and sixteen different organic amendment compositions were tested in a complete randomized design with three replications. Coffee seedling growth biometrics was measured, and R-program was used to calculate the statistical difference at a 5 % significance level. The organic amendment composition with 3:2:1 (topsoil: forest soil: sand) sown at a depth of 2 cm had statistically higher values of seedling stem height, leaf length, and taproot length by 82.82 %, 93.35 %, and 85.41 % than in the topsoil at a depth of 3 cm. Likewise, the main effect of organic amendment with 3:2:1 (topsoil: forest soil: sand) in internode length, number of nodes per seedling stem, number of true leaves per seedling, and leaf width were also higher by 70.42 %, 63.16 %, 92.23 % and 91.80 % than seedlings grown in topsoil solely. Interestingly, the days of 50 % emergence in 3:2:1 (ratio of topsoil: forest soil: sand) organic amendment composition were earlier by 62.11 days than using topsoil. This could be because of the accessibility of a significant quantity of organic carbon, primary macronutrients, alkaline nature of the growth media in addition to having low bulk and particle densities in the forest soil that could increase coffee seedling growth biometrics by improving soil porosity, aeration and nutrient uptake capacity, producing important soil microbes and neutralizing organic acids in comparison with the topsoil.

Extraction and Characterization of Cellulose from Coffee Husk and Brewery’s Spent Grain Fibers Using Alkali-Hydrogen Peroxide Treatment Method

Coffee husk (CH) and brewery spent grain (BSG) fibers are sustainable industrial residues that consist of cellulose. The present study aimed at the extraction of cellulose from CH and BSG fibers and to study the effect of alkali-hydrogen peroxide (5% NaOH–7% H2O2) treatment during the extraction by characterizing the extracted cellulose. Characterization of cellulose particles, such as crystallinity, functional groups, thermal properties, and morphology, was conducted by performing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), and scanning electron microscopy (SEM), respectively. The finding shows that the maximum cellulose yields obtained from CH and BSG fibers are 37.3% and 26.5%, respectively. From the XRD results, the cellulose obtained from CH fiber (C-CH) and from BSG fiber (C-BSG) showed diffractive peaks with the highest intensity of approximately 1,003 and 1,236 counted at 2θ = 22°, respectively. A reduction in the absorption of peaks was observed on the FTIR spectrum for both C-BSG and C-CH samples at different wavelengths. SEM demonstrated that the surface roughness of the celluloses was enhanced. TGA showed that the maximum temperature decomposition observed for both C-CH and C-BSG is 360°C and 380°C, respectively. Generally, in this study, alkali-hydrogen peroxide (5% NaOH–7% H2O2) treatment was effectively used for the treatment of BSG and CH fibers for the extraction and surface modification of cellulose particles. The extracted cellulose in the present study can be used as an alternative to conventional cellulose for the manufacturing of biocomposite materials, preparation of particle boards and furniture, and production of food packaging materials.

Valorization of coffee husks for the sustainable removal of pharmaceuticals from aqueous solutions

ABSTRACT The contamination of wastewater with pharmaceutical compounds represents a growing environmental challenge due to the inefficiency of conventional treatment systems in removing these emerging contaminants. The coffee husk (CH) is a promising bioadsorbent due to its abundant availability as a byproduct of coffee production. This study focuses on using untreated CH as an adsorbent for removing acetaminophen (ACE) and ciprofloxacin (CIP) while exploring the impact of pyrolysis temperature on the adsorption efficiency of these pharmaceutical compounds. The results reveal an excellent CH performance in removing CIP, achieving 64% removal with a maximum adsorption capacity of 37.00 mg/g. Increasing the pyrolysis temperature during the heat treatment of coffee husks significantly affects the adsorption of CIP. This behavior is primarily due to the reduction in functional groups, which are essential for facilitating the adsorption of CIP onto the resulting biochar. Thermodynamic parameters (ΔH° &amp;gt; 0 and ΔG° &amp;gt; 0) indicate that CIP adsorption on CH is an endothermic and not spontaneous process. The removal efficiency of CIP on CH for synthetic wastewater and urine matrices showed that CH can effectively remove CIP from wastewater. Finally, the reuse of CH as a bioadsorbent highlights its potential to contribute to water quality improvement and environmental preservation.

Improved tomato development by biochar soil amendment and foliar application of potassium under different available soil water contents

The use of carbonaceous materials such as biochar has been considered an innovative solution in agriculture, especially to mitigate dry events caused by climate change. Biochar can improve water holding capacity, physical and chemical properties of soil, and increase the productivity of agricultural systems. However, underlying physiological mechanisms remain poorly understood. Mineral supplementation with potassium nitrate (KNO3) via foliar application is another promising strategy in agricultural management under irrigation deficit. Thus, we investigated the combined effects of biochar and foliar application of KNO3 on growth, yield, and physiology of tomato plants under different irrigation regimes. Results did not indicate a synergistic effect of biochar and foliar application of KNO3. Biochar application alleviated tomato plant stress under deficit irrigation, with plants showing better functioning of photosynthetic apparatus, higher yield, and better fruit quality, as well as increased water use efficiency. Coffee husk biochar (K-rich feedstock) fully met the tomato plant’s demand for K and partially met the demand for some other elements (P, Mg, Fe, Zn, Mn, and Cu). Although positive effects of KNO3 application was verified for some physiological and fruit quality components, overall, foliar application of KNO3 did not improve tomato yield. It is concluded that biochar soil amendment can be a promising practice to increase yield and quality of tomato fruits under deficit irrigation. Therefore, biochar-based fertilizer can be an alternative K source that also provides stable carbon to soil and helps to mitigate stress caused by prolonged drought.

Magnetic iron‐oxide coffee husk and khat waste biochar nanocomposites for removal of methylene blue from aqueous solution

AbstractWastewater from the textile and dyeing industries contains hazardous dyes. This study aims to determine the effectiveness of magnetic biochar nanocomposites synthesized from khat leftovers (KLs) and coffee husks (CHs) in removing methylene blue (MB) from wastewater. Magnetic biochar nanocomposites were synthesized by pretreating 25 g of biomass with a 12.5 mmol mixture of FeS and FeCl3 at a 1:1 molar ratio, followed by pyrolyzing at 300°C for 1 h. The resulting products were analyzed using X‐ray diffraction, Fourier transform infrared, scanning electron microscope, and Brunauer‐Emmett‐Teller. The results showed that the adsorbents are amorphous, and the activated biochars, are more porous and contain various functional groups such as C‐O, C = C, O‐H, C‐H, and Fe‐O. When 0.2 g of pristine biochars of CH and KL were applied to 20 mL aqueous solutions containing 20 mg/L of MB at pH 7.5 and 25°C, they removed 44.73% and 75.26% of MB, respectively. However, the resulting nanocomposites exhibited a maximum removal efficiency of 99.10% and 99.23% with magnetic iron oxide‐CH biochar nanocomposite (Fe3O4‐CHBNC) and magnetic iron oxide‐KL biochar nanocomposite (Fe3O4‐KLBNC), respectively, with maximum adsorption capacities of 51.02 and 78.13 mg/g. The reusability study also showed removal efficiencies of 77.57% and 83.49% up to six‐cycle reuse.

Novel foods, food enzymes, and food additives derived from food by-products of plant or animal origin: principles and overview of the EFSA safety assessment.

The European Union (EU) is committed to transitioning toward a circular economy model, with food waste being one of the areas to be targeted. To close the loop of food waste generated during food processing and discarded at the retail or consumption phases, research and innovation parties proposed to valorize agro-food by-products to produce novel foods and food improvement agents (food additives, food enzymes, and food flavorings). In the EU, the authorization of such novel foods and food improvement agents is governed by different regulatory frameworks. A centralized safety assessment by the European Food Safety Authority (EFSA) is the prerequisite for their authorization through the so-called Union Lists. Up to December 2023, EFSA published 45 scientific opinions on the safety of novel foods, food enzymes, and food additives derived from by-products of plant and animal origin. The current study illustrates examples of these by-products for the production of novel foods or food improvement agents and the data requirements behind their respective safety assessments conducted by EFSA. In this review, applications on novel foods, food enzymes, and food additives received by EFSA were screened and analyzed to find the common scientific requirements and differences in terms of the safety evaluation of such products. Various by-products (i.e., corncobs, coffee husks, spent grains of barley and rice, grape pomace, pumpkin peels, bovine whey, eggshells, shrimp heads, and animal organs or tissues) were described in the applications as being processed (extraction, physical treatments, and chemical and enzymatic reactions) to obtain novel foods and food improvement agents. The heterogeneity and complexity of these products emphasize the challenge of their safety assessment, depending on the characteristics of each product. However, as this study shows, the scientific requirements underpinning their safety do not differ substantially in the different regulated product areas considered, with similar information needed to assess their safety in terms of identity, production process, compositional characterization, proposed/intended uses and exposure assessment, toxicological information, and allergenicity data. Additional nutritional information and data on the history of use are required in the case of novel foods.

Synthesis of Zinc Oxide Nanoparticles Based on Coffee Husks Embedded on Mesoporous Silica for the Sensing of Acetaminophen

AbstractIn the present work, a green method improved by surface response methodology (SRM) has been used for the synthesis of zinc oxide nanoparticles (ZnONPs) from coffee husks extract, in which Santa Barbara‐15 (SBA‐15) mesoporous silica has been embedded. The composite formed has been drop coated on bare glassy carbon electrode and the resulting sensor (ZnONPs/SBA‐15/GCE) was used for the sensing of acetaminophen (ACT). Reaction factors such as pH, incubation time and precursor concentration were optimized during nanoparticles synthesis using SRM. The synthesized nanoparticles and the composite were characterized by ultraviolet‐visible spectrophotometry (UV‐Vis), Fourier transform infrared (FTIR) spectroscopy, powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX/EDX‐mapping) analysis, thermogravimetry analysis/differential thermogravimetry (TGA/DTG), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), showing the good elaboration of ZnONPs/SBA‐15/GCE. After optimization of parameters susceptible to affect the detection limit of ACT, the calibration curve was plotted from 4 μM to 32 μM, showing good linear response with a detection limit of 0.11 μM. The developed sensor shows good sensitivity, reproducibility, repeatability and storage stability at room temperature and was successfully applied for the determination of ACT in pharmaceutical sample.

Enhancing Biodegradability of Coffee Husk and Water Hyacinth Using Food Waste: Synergistic and Kinetic Evaluation Under Co-digestion

Enhancing Biodegradability of Coffee Husk and Water Hyacinth Using Food Waste: Synergistic and Kinetic Evaluation Under Co-digestion

Feasibility study of coffee husk char-derived carbon dots to enhance solar photovoltaic-thermal applications

Coffee is one of the most traded commodities in the world. Coffee husk makes up the majority of the solid debris generated during the dry processing of coffee, which is between 30% and 50%. Pyrolysis is a reliable and feasible technology to valorise the coffee husk. The present study proposes and investigates a novel method for producing carbon dots from coffee husk char through pyrolysis. Nanomaterials are becoming more popular to improve the thermal and optical properties of working fluids used in solar photovoltaic and thermal conversion systems. The coffee husk-char derived carbon dot (CHC-CD) nanofluids are prepared with different char concentrations (1%, 2%, 3% and 4%). The chemical and optical properties of the nanofluid produced from coffee husk char (CHC-CD nanofluid) are investigated. The morphology, size and particle size distribution of the CHC-CD particles were studied using field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The particles were found to have an average size of 5.38 nm. The CHC-CD nanofluid had a basic pH and negative zeta potential, which was found to decrease with an increase in the char concentration and pH. The nanofluid prepared with 2% char was found to have a zeta potential of −61.4 mV. It was evident from the UV–vis transmittance spectra that the CHC-CD nanofluid prepared with a char concentration of 2% had very limited transmittance in the UV region and good transmittance above 735 nm. This transmittance range is found to be favourable for the smooth and efficient operation of silicon-based solar PV cells. The CHC-CD nanofluid also showed a maximum intensity emission wavelength of 522 nm at an excitation wavelength of 450 nm. Characterisation of the carbon phase, surface functional groups, and surface defects was also done using XRD, FTIR, and Raman spectroscopy, respectively. The optical and chemical properties indicate that the developed CHC-CD nanofluid can find application not only in solar photovoltaic and thermal systems but also in applications in biomedical and chemical sensor applications.

Potencial Citric Acid Production by Fungi Using Hemicellulosic Hydrolysate of Coffee Husk as Substrate

Objective: The aim of this experimental assay was to produce citric acid via submerged fermentation, using hemicellulose hydrolysate from coffee husks as main substrate. Theoretical framework: Obtaining citric acid through fermentation processes, especially submerged fermentation, has become viable due to the use of low-cost materials, such as industrial subproducts derived from green biomass. Methodology: The hemicellulose hydrolysate was obtained from the acid hydrolysis process of the coffee husk. The strains of the fungi Aspergillus niger, Aspergillus westerdijkiae and Rhizopus sp. were employed to carry out the fermentation assays. A bioreactor consisting of a 500 ml flat-bottomed flask was used, with an inlet for supplying air and an outlet for removing samples Results and Conclusion: The obtained results showed an increase in number of spores of the studied fungi as well as citric acid accumulation during the first 72 h of fermentation. On the other hand, after 96 h of fermentation citric acid concentration began to decrease indicating its consumption by the studied fungi, probably due to the lack of nitrogen sources and the cellular stress caused by the mixed composition of the hemicellulose hydrolysate. Implications of the research: There is a need to study the interaction between the nitrogenous nutrients to be added to the fermentation medium and the concentration of reducing sugars as the sole carbon source in the lignocellulosic hydrolysate. Originality/value: This work highlights the potential production of citric acid by fungi using a coffee husk as a renewable biomass.