Orange Residue Research Articles

Citric acid production by Brazilian garlic Aspergillus welwitschiae strains using orange residues

The global production of citrus fruits has expressively grown resulting in large amounts of residue. Orange residues are rich in carbon and could be used as substrates for production of biomolecules such as citric acid. In this study, wild and mutant Aspergillus welwitschiae strains isolated from Brazilian garlic were used to produce citric acid from orange residues, using solid-state fermentation. The results showed that the mutant A. welwitschiae UELAs 15.262/35 produced great amount of citric acid in the fourth day of solid-state fermentation using total and reducing sugars and producing cellulases. On the other hand, there was no production of citric acid by wild A. welwitschiae UELAs 15.262. The use of total and reducing sugars and the production of cellulases by A. welwitschiae UELAs 15.262 were detected, suggesting the use of carbon sources for the production of other metabolites. The great use of reducing sugars and cellulases production by A. welwitschiae UELAs 15.262/35 indicated the consume of carbon sources from the orange residue to produce citric acid at early times of fermentation. These findings lead to the possibility of biotechnological valorization of orange residues for acid organic production by A. welwitschiae strain.

The effect of carbon coating on the arsenite sorption by magnetic carbon nanocomposites

AbstractArsenic pollution has emerged through anthropogenic activities and natural mineral leaching processes. This study aims to advance the use of magnetic carbon nanocomposites (MCNs) in the sorption of arsenic, studying the influence of feedstock and the presence of carbon coating on magnetic nanoparticles. Previous works have shown that post-pyrolysis treatment improves the stability of MCNs by reducing iron leaching due to the formation of a carbon coating that encapsulates the iron oxide nanoparticles. However, this carbon coating could influence the adsorption properties of MCNs. This investigation deals with arsenic adsorption by four MCNs prepared by co-precipitation of magnetite (Fe3O4) nanoparticle into four carbonaceous matrixes, followed by a post-pyrolysis treatment. The pristine carbonaceous matrixes used in the present work were commercial activated carbon (CAC), charcoal (CC), hydrochar from the orange residue (HCOR), and biochar from sunflower husk (BCSFH). Pristine carbonaceous materials and MCNs without post-pyrolyzed were also used as arsenic sorbents in water solutions. Additionally, kinetic studies were carried out to explore the sorption properties of different MCNs and pristine materials, concerning the removal efficiencies (expressed as a percentage) and adsorption capacities, determining the equilibrium time. The results demonstrated that the presence of magnetite increases the adsorption of arsenic, being higher in the case of materials obtained by direct co-precipitation than in materials subjected to a post-pyrolysis process. The presence of a carbon layerprotecting the magnetite slightly decreases the adsorption of arsenic.

Evaluation of Different Pectic Materials Coming from Citrus Residues in the Production of Films.

This article explores the use of citrus residues as a source of different pectic materials for packaging film production: a water-soluble orange residue extract (WSE) (~5% pectin), semi-pure pectins extracted in citric acid (SP) (~50% pectin), and commercial pure citrus pectins (CP). First, these materials were characterized in terms of chemical composition. Then, films were produced using them pure or mixed with chitosan or glycerol through solvent-casting. Finally, antioxidant activity, functional properties (e.g., mechanical and gas barrier properties), and visual appearance of the films were assessed. WSE films showed the highest antioxidant activity but the lowest mechanical strength with the highest elongation at break (EB) (54%); incorporating chitosan increased the films' strength (Young's modulus 35.5 times higher). SP films showed intermediate mechanical properties, reinforced by chitosan addition (Young's modulus 4.7 times higher); they showed an outstanding dry O2 barrier. CP films showed a similar O2 barrier to SP films and had the highest Young's modulus (~29 MPa), but their brittleness required glycerol for improved pliability, and chitosan addition compromised their surface regularity. Overall, the type of pectic material determined the film's properties, with less-refined pectins offering just as many benefits as pure commercial ones.

Productive and Ruminal Microbiological Behavior of Sheep Fed with Two Levels of Dehydrated Orange Residue

Objective: To evaluate the productive and ruminal microbiological behavior of sheep fed with two levels of dehydrated orange residue (DOR). Design/methodology/approach: Thirty Dorper x Katahdin crossbred male sheep with an average live weight of 22 ± 1.0 kg were distributed in a completely randomized design, with three treatments and ten repetitions. The distribution of treatments was as follows: T1 = diet with 0% DOR (control), T2 = diet with 15% DOR, and T3 = diet with 30% DOR. The variables evaluated were daily weight gain, dry matter intake, feed conversion, ruminal pH, and microbiological analysis. Results: There were no significant differences (p>0.05) in the productive variables due to the inclusion of DOR in the diet. Similarly, the concentration of ruminal microorganisms did not present significant differences between treatments. Study limitations/implications: The study did not include an economic analysis that would demonstrate a reduction in production costs by decreasing the inclusion of maize in the diet. Conclusions: Maize grain is one of the most commonly used cereals as an energy source in sheep feeding; however, it can be replaced by DOR up to 30% without affecting the productive and ruminal microbiological variables in fattening sheep.

Fractionation of orange lignocellulosic biomass and optimization of distinct methods for oil extraction

Abstract Annually, amounts of orange waste are directed into the environment. The orange waste oil is a potential source of compounds of interest and alternatives have been explored to highlight their potential. Appropriately, this study investigated the effects of oil extraction processes involving pressurized liquids (PLE) and supercritical CO2 (SC-CO2) on orange residues. The results were compared with the standard Soxhlet procedure. The optimization of the operational parameters was established based on the adjustment of different process conditions for pressure (150 and 350 bar), extraction time (20 and 60 min), and temperature (40 and 60 °C). The results indicated that the maximum oil yields for orange peel and pomace were 37.76 % and 43.39 %, respectively, for the PLE approach. The SC-CO2 expressed maximum yields of up to 0.50 % and 0.38 % for peel and pomace, respectively. The GC-MS analysis reported the concentration of bioactive compounds after the distinct extraction methods.

Sustainable pectin-based film for carrying phenolic compounds and essential oil from Citrus sinensis peel waste

Currently, food science faces the challenge of finding methods to deliver functional and nutritional compounds in ready-to-eat products. Biopolymeric films enriched with essential oils are an emerging strategy for incorporating valuable components into edible carrier matrices. This study investigated the wastewater from orange peel hydrodistillation as a source of phenolic compounds and an innovative ingredient to develop bioactive limonene-loaded pectin-based films, addressing waste disposal challenges by developing a multi-functional packaging material. The objective was to evaluate the effects of formulation synergies, particularly pectin-phenolic interactions, on the physicochemical, rheological properties, and essential oil retention capacity of film-forming emulsions, and then assess the effects on the physicochemical and mechanical properties of the films. Films were analyzed for morphology, water vapor permeability, light transmittance, mechanical, chemical, and physical properties, and encapsulation efficiency. Three formulations were evaluated: pectin control (PC), pectin with Tween-80 surfactant (PT), and pectin with phenolic-rich wastewater (PPW). PPW emulsions displayed higher viscosity, consistency, kinetic stability, and essential oil retention compared to PC. The resulting environmentally-friendly films exhibited increased thickness, improved oil droplet distribution, a more crystalline structure, lower clarity, better flexibility, and increased water vapor permeability. Altered FTIR spectrum bands suggested potential pectin-phenolic interactions, influencing film physicochemical properties through mechanisms such as enhanced crosslinking. The PT film-forming emulsion demonstrated lower kinetic stability and less homogeneity than PC and PPW, showing that the use of the commercial surfactant (0.1g/100 g of film-forming emulsion) led to less favorable performance in terms of emulsion stability and film properties compared to PPW and PC. Conclusively, utilizing orange residue for bioactive pectin-based films offers valuable insights for promoting shelf life, reducing the need for formulation surfactants, and adding nutritional value in food applications, while simultaneously repurposing underutilized waste. This research also contributes to insights into the development of more stable emulsions for creating uniform films.

Performance Analysis of Waste Biomass Gasification and Renewable Hydrogen Production by Neural Network Algorithm

Abstract This study assesses renewable hydrogen production via gasification of residual biomass, using artificial neural networks (ANNs) for predictive modeling. The process uses residues from sugarcane and orange harvests, sewage sludge, corn byproducts, coffee remnants, eucalyptus remains, and urban waste. Simulation data from aspen plus® software predict hydrogen conversion from each biomass type, with a three-layer feedforward neural network algorithm used for model construction. The model showed high accuracy, with R2 values exceeding 0.9941 and 0.9931 in training and testing datasets, respectively. Performance metrics revealed a maximum higher heating value (HHV) of 18.1 MJ/kg for sewage sludge, the highest cold gas efficiency for urban and orange waste (82.2% and 80.6%), and the highest carbon conversion efficiency for sugarcane bagasse and orange residue (92.8% and 91.2%). Corn waste and sewage sludge yielded the highest hydrogen mole fractions (0.55 and 0.52). The system can reach relative exergy efficiencies from 24.4% for sugarcane straw residues to 42.6% for sugarcane bagasse. Rational exergy efficiencies reached from 23.7% (coffee waste) to 39.0% (sugarcane bagasse). This research highlights the potential of ANNs in forecasting hydrogen conversion and assessing the performance of gasification-based renewable hydrogen procedures using biomass wastes.

Waste-Derived Fertilizer Acts as Biostimulant, Boosting Tomato Quality and Aroma

Tomato quality is intricately regulated by a combination of factors, including the presence of bioactive compounds referred to as secondary metabolites and various organoleptic characteristics. These attributes are notably influenced and harmonized by the specific growing conditions, with a particular emphasis on the type of fertilization employed. Traditionally, chemical fertilizers have been favored in crop cultivation due to their cost-effectiveness and ability to accelerate crop growth. However, in pursuit of sustainable and intelligent agricultural practices, there is a growing need for alternative fertilizers. In this context, the present study aimed to assess the impact of fertilizers derived from waste materials, specifically sulfur bentonite and orange residue (referred to as SB), on tomato quality. This assessment extended to examining qualitative and quantitative alterations in aroma-related volatile compounds and the antioxidant systems of tomatoes, in comparison to the conventional use of fertilizers such as horse manure (HM) and nitrogen, phosphorus, and potassium (NPK). The results obtained revealed distinct effects of different fertilizers on tomato quality. Notably, parameters such as TPRO (total protein), TCARB (total carbohydrate), LIC (lycopene content), TCAR (total carotenoid content), total phenols (TPHE), total flavonoids (TFLA), and aroma profiling exhibited significantly superior values in the group treated with sulfur bentonite (SB) fertilizer. These findings strongly suggest that the novel fertilizer functioned as a biostimulant, enhancing the nutraceutical and sensory attributes of tomatoes, with a pronounced impact on the synthesis of secondary metabolites and the aroma profile of the fruits.

Influence of orange residue content on Sol-gel synthesis of cobalt ferrite Nanoparticles: Morphological and magnetic properties

Cobalt ferrite was successfully produced from nitrates using, as a precursor, 20, 40 or 60 g.L-1 of orange residue in water, followed by calcination at 973, 1073, or 1173 K for 6 h. Fourier transform infrared spectroscopy indicates that the increase in carbonyl-related peak content in the precursor bath due to a higher concentration of orange particulate favors the reaction of nanocrystals' formation. Rietveld's analysis of x-ray diffraction data indicates that the percentage of cobalt ferrite tends to increase with the concentration of orange residue, whereas grain size increases with calcination temperature. The concentration of cobalt ferrite is 99% for samples produced with 60 g.L-1 of orange particulate, a novel achievement for green synthesis using an industrial residue as a precursor. Magnetic anisotropy, obtained from ferromagnetic resonance measurements, scales with the crystalline grains' size, being dependent on calcination temperature, regardless of orange particulate precursor concentration.

Effects of fertilizer produced from agro-industrial wastes on the quality of two different soils

ABSTRACT A newly developed sustainable fertilizer, known as SB, was created by blending organic and mineral components using agro-industrial waste, sulphur, and orange residue, bound together with bentonite. It was extensively tested on two distinct soils with different chemical and biological properties, comparing its effectiveness to traditional chemical (NPK) and organic (horse manure, HM) fertilizers, with unfertilized soil as a control (CTR). The introduction of SB did not alter soil texture but significantly impacted soil chemistry and biology. It positively influenced the labile fraction of soil organic matter, resulting in a 15% increase in soil microbial biomass, total phenolic content, cations, bacterial colonies, and enzyme activities, with varying effects depending on soil characteristics. SB demonstrated a beneficial effect on both soil types, with optimal concentrations determined to be 2.8 for Motta and 4.2 for Lazzaro, highlighting the importance of soil characteristics in fertilizer effectiveness. In conclusion, SB represents a promising innovation for transitioning from traditional agriculture to a more sustainable and circular approach, offering economic and environmental benefits by reducing waste disposal costs and decreasing reliance on mineral fertilizers in line with circular economy principles. This study emphasizes the need to consider soil properties when optimizing fertilizer use.

Enhancement of volatile fatty acids production through anaerobic co-digestion of navel orange residue and waste activated sludge: Effect of pre-treatment and substrate proportions

In this study, the co-digestion system with Navel orange residues (NOR) and Waste activated sludge (WAS) was established, by pre-treating the NOR and setting different volatile solids (VS) ratios of NOR to WAS to motivate the production of volatile fatty acids (VFA). The pre-treatment method (pH 7 and temperature 70 °C) promoted the release of dissolved organic matter, and the concentration of soluble chemical oxygen demand (SCOD) increased by 45.56% compared with the untreated group (pH 3 and temperature 20 °C). In the co-digestion system, the highest VFA yield (5716.69 mg/L) was obtained at VS ratio of 2. When the VS ratio was increased to 4, the imbalance in proportions of carbon and nitrogen affected VFA production, and the high concentration of essential oils (EO) present in the NOR inhibited the methane production; the cumulative yield of methane gas decreased by 24.10% compared with the yield obtained when the VS ratio was 2. Analysis of microbial community revealed that an increase in the number of VFA-producing microbial populations and the abundance of Methanobacteria resulted in the accumulation of acetic acid. This study demonstrated that co-digestion of NOR with WAS improve VFA production, thus realizing the utilization of solid wastes and reducing environmental pollution.

Production of AC from Bamboo, Orange, and Paulownia Waste-Influence of Activation Gas and Biomass Maturation.

The production of agricultural waste is associated with environmental problems and risks to public health. The general interest demands, as an ecological alternative, the proper management of waste generated by industrial activity through its transformation into value-added products. Carbonization/activation (2 h/2 h) at 700 °C in a vertical furnace (20 K/min), to produce biochar and activated carbon (AC) from bamboo, orange, and paulownia residue, was carried out in a laboratory facility with physical activation by CO2 and steam. The characterization of the carbonaceous material obtained was based on the determination of the N2 adsorption-desorption isotherms at 77 K, the specific surface area with the BET procedure, and its internal structure by means of SEM images. The BET surface area values obtained as a function of the CO2/steam agent used were 911/1182 m2/g, 248/388 m2/g, and 800/1166 m2/g for bamboo, orange, and paulownia, respectively. The range of variation of porosity in paulownia residue generated after steam activation was 485-1166 m2/g, varying depending on the degree of maturity of the biomass used. Research has shown that both the type of activation agent used to produce AC and the degree of plant maturation of the precursor residue affect the quality and characteristics of the final product.

Valorization of food wastes with a sequential two-step process for microbial β-carotene production: A zero waste approach

Here, two consecutive β-carotene fermentation processes were carried out with Rhodotorula glutinis yeast in the growth media obtained from orange and grape wastes. Firstly, waste biomasses were subjected to hot water extraction. Effects of waste type, drying pretreatment, particle size and solid/liquid ratio on the total concentration and yield of sugars recovered were tested. The highest sugar concentration was obtained by the hot water extraction of fresh grape pomace as 61.2 g total reducing sugars (TRS)/L at a solid/liquid ratio of 100 g/L. In the first fermentation process, effect of solid/liquid ratio (initial TRS concentration) on β-carotene production pattern of R. glutinis was investigated in the media obtained directly by hot water extraction of the wastes. Microorganism and β-carotene concentrations increased with increasing solid/liquid ratio (range 10–100 g/L), and the microbial growth data fit the Monod model well for all cases. Maximum β-carotene concentration in the growth medium obtained from hot water extraction of 100 g/L of grape pomace was determined as 5988.6 mg/L. In the second fermentation process, β-carotene was produced in the acid hydrolysate of extraction residues. 10.1 g/L and 6.7 g/L of TRS was obtained after acid hydrolysis of orange and grape residues, respectively, and the highest β-carotene concentration of 370.0 mg/L was found in the medium of hydrolyzed orange peel extraction residue. Total β-carotene production increased to 1777.1 and 3279.6 mg/L (26% and 4.9% of increase) after the second fermentation step. 85.3% and 80.2% of reduction in orange and grape waste weights were observed at the end of the process, which was an indicator of efficient waste biomass disposal. Two sequential β-carotene fermentation steps offered significant advantages in terms of both efficiency and a zero waste approach.

Activity of endophytic fungi in enantioselective biotransformation of chiral amines: New approach for solid-state fermentation

Oranges are among the most consumed fruits in Brazil, with over 80 million tons production per year. Currently, one of the main uses of orange residues is to supplement animal feeds. However, orange residues can be used in other ways, including for obtaining enzymes. However, for the pyridoxal 5-phosphate (PLP)-dependent enzyme group, which catalyze transamination reactions, no work has been described. The use of orange-peel residues for solid-state fermentation using endophytic microorganisms is a new and interesting approach to produce these enzymes at lower cost compared to the use of purified enzymes associated to PLP co-factor. In the batch process developed in this study, it was possible to achieve a maximum conversion of 49% after 48 h of incubation, an enantiomeric excess of 99% (R)-1,2,3,4-tetra-hydro-1-naphthylamine, and productivity of 0.0102 mg biocatalyst.h−1, using the solid enzyme preparation from Alternaria arborescens as biocatalyst. In a continuous-flow system, 51% conversion and >99% ee of (R)-1,2,3,4-tetra-hydro-1-naphthylamine were achieved, with a six-fold increase productivity (0.0625 mg biocatalyst.h−1). We have screened different fungi samples for transaminase activity and we found a hit for solid-state fermentation. The endophytic fungus genetically identified as Alternaria arborescens showed promising results for the transaminase activity on the kinetic resolution of chiral amine blocks. Therefore, along with other improvement of the biocatalytic toolbox for chiral amines synthesis, we have found that the solid enzymatic preparation of the endophytic fungus Alternaria arborescens could accept bulky substrates with reasonable activity, compared to the wild-type transaminase already published over literature, and, with high enantioselectivity.

Caracterización de las harinas de trigo (Triticum aestivum), y de residuo de naranja (Citrus x aurantium) y de manzana (Malus domestica) para su aplicación en alimentos

Flours were produced from orange and apple residues (peel). Subsequently, their proximate composition, dietary fiber, particle size, microbiological analysis and color coordinates (L*, a* and b*) were evaluated. The results revealed that the orange residue meal (HRN) and apple residue meal (HRM) have a high fiber content (> 37%) and in the granulometry, 72% retention was obtained in a 425 µm mesh for both HRN and HRM. Regarding color coordinates, the highest values were L* (91.44) for HT, a* (6.51) for HRM and b* (22.66) for HRN. Finally, all flours meet the microbiological requirements established by local regulations. The waste flour has a similar energy value to wheat flour and other conventional flours, so this study revealed that flours produced from orange and apple peel, which are generated in large quantities as agro-industrial by-products, can be used as alternative ingredients in various sectors of the food industry.

Influence of post-pyrolysis treatment on physicochemical properties and acid medium stability of magnetic carbon nanocomposites

This study presents the preparation of magnetic carbon nanocomposites (MCNCs) through a two-step procedure: (i) in situ co-precipitation of magnetite (Fe3O4) nanoparticles into four different carbonaceous matrixes and (ii) post-pyrolysis treatment to coat the magnetic core. Four post-pyrolysis MCNCs were obtained: MACP (post-pyrolyzed magnetic activated carbon), MCCP (post-pyrolyzed magnetic charcoal), MHCPOR (post-pyrolyzed magnetic hydrochar from orange residue), and MBCPSFH (post-pyrolyzed magnetic biochar from sunflower husk). These four samples were compared with the starting MCNCs prepared without post-pyrolysis treatment: MAC, MCC, MHCOR, and MBCSFH, respectively. After post-pyrolysis treatment, a thin carbon layer surrounding some of the magnetite nanoparticles was identified by transmission electron microscopy. Post-pyrolysis modified the porous structure and chemical composition of MCNCs. Furthermore, a leaching test with acid sulfuric solution at 90 °C was carried out. The results suggested that the MHCPOR and MBCPSFH were more stable in an acidic medium than MACP and MCCP, indicating that the coat generated during post-pyrolysis of hydrochar and biochar could partially protect the magnetic core by reducing Fe leaching into the aqueous solution. Biochar and the hydrochar-based MCNCs before and after post-pyrolysis treatment exhibit superparamagnetic properties; however, their saturation magnetization (Ms) decreased considerably. These results open the potential application fields of MCNCs obtained by post-pyrolysis of biochar and hydrochar-based materials in acidic mediums.

Phytochemicals from Red Onion, Grown with Eco-Sustainable Fertilizers, Protect Mammalian Cells from Oxidative Stress, Increasing Their Viability.

Red onion, a species of great economic importance rich in phytochemicals (bioactive compounds) known for its medicinal properties, was fertilized with sulphur-bentonite enriched with orange residue or olive pomace, with the aim of producing onion enriched in health beneficial compounds. There is a worldwide great demand of minimally processed food or food ingredients with functional properties because of a new awareness of how important healthy functional nutrition is in life. Phytochemicals have the capacity to regulate most of the metabolic processes resulting in health benefits. Red onion bioactive compound quantity and quality can vary according to cultivation practices. The main aims of the current research were to determine the chemical characteristics of the crude extracts from red onion bulbs differently fertilized and to evaluate their biological activity in normal and oxidative stress conditions. The lyophilized onion bulbs have been tested in vitro on two cellular models, i.e., the H9c2 rat cardiomyoblast cell line and primary human dermal fibroblasts, in terms of viability and oxygen radical homeostasis. The results evidenced different phytochemical compositions and antioxidant activities of the extracts obtained from red onions differently fertilized. Sulphur-bentonite fertilizers containing orange waste and olive pomace positively affected the red onion quality with respect to the red onion control, evidencing that sulphur-bentonite-organic fertilization was able to stimulate plant a secondary metabolism inducing the production of phytochemicals with healthy functions. A positive effect of the extracts from red onions treated with fertilizers—in particular, with those containing orange waste, such as the reduction of oxidative stress and induction of cell viability of H9c2 and human fibroblasts—was observed, showing a concentration- and time-dependent profile. The results evidenced that the positive effects were related to the phenols and, in particular, to chlorogenic and p-coumaric acids and to the flavonol kaempferol, which were more present in red onion treated with low orange residue than in the other treated ones.

A Comparison of Microbial Communities of Mango and Orange Residues for Bioprospecting of Biosurfactant Producers

Plants and their derivatives, such as fruits, can be inhabited by different bacteria. However, this microbiota is still poorly studied. Among the wide variety of metabolites that bacteria produce, biosurfactants have been identified as potential molecules in the development of bioprocesses for various industrial sectors. In this work, we analyzed and compared the microbiota of fruit residues (mango and orange), in order to compare two possible sources of bioprospecting. For this, a bioinformatics approach was used to perform the taxonomic analysis and the prediction of the functional profile of the microbiota present in the samples. The results showed that the microbiota present in both fruit residues have the potential in biotechnological applications to produce biosurfactants, as these microbiota have genes related to the biosynthesis of these compounds. The common core of the microbiota present in the samples—Stenotrophomonas, Klebsiella, Serratia and Citrobacter—proved, according to the literature, to be composed of biosurfactant producers, showing the biosurfactant potential of the bacteria isolated from orange and mango residues.

Production of single cell protein from orange peel residues by Candida utilis

Orange residues are an excellent carbon and energy source to obtain high added value compounds through bioprocessing, such as single-cell protein (SCP). This study aims to evaluate the orange peel as the only carbon and energy source for the growth of Candida utilis and evaluate and optimize the SCP production by submerged fermentation. A comparison of three fermentation media was made using different mineral salts and orange peel as the sole carbon source (10%), where each medium was inoculated with 1 × 106 cells of C. utilis at the same conditions of 150 rpm at 30 °C for 96 h. Optimization was carried out with a Box Bencken 33 design. The results showed that orange peel is an excellent source of nutrients, especially in total carbohydrates and minerals such as calcium and potassium. The fermentation results showed greater yeast growth when using Medium 1, obtaining 13.42 g L-1 of biomass. In addition, Candida utilis has the higher consumption of total sugars and reducing sugars in the medium 1 with 81 and 89%, respectively. Optimization of the medium and fermentation conditions was achieved, obtaining 15.71 g L-1 and 6.22% of biomass and total protein, respectively. Therefore, the orange peel is an agro-industrial waste with the potential to be used as a carbon source for the growth of C. utilis.

Silage as a pre-treatment of orange bagasse waste to increase the potential for methane generation

Among the various methods of pre-treatment of lignocellulosic waste with the objective of optimizing the production of methane, silage stands out as a promising alternative due to its operational simplicity, low cost and effective results. In this work, the silage of orange waste (Citrus cinensis) with 14 and 21 days and its influence on the potential of methane generation was evaluated, also evaluating the impacts of silage on the kinetics of the process. Among several configurations of substrate and inoculum studied, the best configuration observed was using the ensiled residue with 21 days and granular anaerobic sludge (ENS21 + GS), reaching a methane generation potential of about 171 N mL·g−1 VS, increasing by 119% in terms of methane generation potential without silage pre-treatment (WENS+GS), obtaining biogas with 70% in CH4. In relation to the kinetics, the silage process drastically interfered in the kinetic behavior of the methane production, being the Cone model the one that obtained the best adjustments, among those studied, for the orange bagasse residue in the evaluated experimental conditions. Silage is an attractive alternative to increase the production of methane for lignocellulosic waste, as a pre-treatment, without significantly increasing operating costs, and it can also be associated with other sequential processes to take advantage of the maximum energy potential of lignocellulosic waste.