https://hdl.handle.net/10259/4244 Wed, 14 Oct 2026 21:36:41 GMT 2026-10-14T21:36:41Z https://hdl.handle.net/10259/12221 Valorization of okara into proteins and fermentable sugars through reduced-pressure alkaline pre-treatment Barea Gómez, Pedro; Sanz Díez, Mª Teresa; Illera Gigante, Alba Ester; Candela Gil, Helena; Queiroz, Sarah S.; Cabrera, Camilo; Mussatto, Solange I. Okara, a soybean by-product from soymilk and tofu production, is generated in large amounts, with approximately 1.1–1.2 kg of wet okara produced per kg of soybean processed. For example, Frias Nutrición (Burgos) produces 7700 tons annually, contributing to approximately 14 million tons worldwide. Due to its high moisture content, storage is costly, requiring drying to prevent spoilage. Discarding it would a significant loss of valuable proteins and fiber. Valorizing okara, especially by recovering proteins and sugars from fiber, without drying pretreatment, would significantly reduce costs and enhance sustainability. The first step to valorize okara was protein hydrolysis using reduced-pressure alkaline pretreatment (RPAP), varying pressure, time, and NaOH concentration. Two optimal conditions were identified at 70 °C using 5 % okara (w/v): (A) 455 mbar, 180 mM NaOH for 1 h (77 ± 3 % yield), and (B) 300 mbar, 100 mM NaOH for 2 h (75 ± 1 % yield). Techno-economic assessment identified process B as more efficient and sustainable at industrial scale. Residual solids from both extractions were subsequently subjected to enzymatic hydrolysis with Cellic® CTec2 (40 FPU/g biomass at 5 % and 10 %), releasing a high content of simple sugars. These hydrolysates were used for lactic acid fermentation with Ligilactobacillus salivarius ATCC 11742 to assess their suitability as substrates. Each hydrolysate was tested alone, supplemented with salts and nitrogen sources typical of MRS medium, and compared to MRS itself. The supplemented hydrolysates showed nearly identical performance to the ideal medium, confirming their suitability for fermentation without inhibitory effects. Trabajo presentado en: XVI International Scientific Agriculture Symposium "Agrosym 2025", Jahorina, Bosnia and Herzegovina, October 2-5, 2025 Wed, 01 Jan 2025 00:00:00 GMT https://hdl.handle.net/10259/12221 2025-01-01T00:00:00Z https://hdl.handle.net/10259/12220 Natural deep eutectic solvents as green pretreatment agents in the biocascade processing of onion peel waste Benito Román, Oscar; Candela Gil, Helena; Barea Gómez, Pedro; Illera Gigante, Alba Ester; Melgosa Gómez, Rodrigo; Beltrán Calvo, Sagrario; Sanz Díez, Mª Teresa In alignment with circular economy principles and the sustainable valorisation of biomass, this work addresses an intermediate stage in a novel green biocascade strategy aimed at converting onion peel waste, an abundant agro-industrial by-product, into cellulose nanofibers. At this stage, the process focuses on the selective removal of non-cellulosic structural components to enrich the cellulose fraction within the lignocellulosic matrix. To achieve this objective, Natural Deep Eutectic Solvents (NADES) were employed as environmentally benign alternatives to conventional toxic solvents for the pretreatment step. A systematic screening was conducted to evaluate various combinations of hydrogen bond acceptors (HBAs), such as choline chloride and betaine, with different hydrogen bond donors (HBDs), primarily organic acids. Key operational parameters, including temperature, NADES-to-onion peel ratio, HBA:HBD molar ratio, and reaction time (up to 10 hours), were thoroughly investigated. Among the tested formulations, choline chloride:lactic acid (ratio 1:2) and choline chloride:tartaric acid (ratio 1:2) mixtures demonstrated the most promising performance, operating effectively at temperatures between 100 and 120 ºC. Under these conditions, and after 6 hours of processing time, an increase in cellulose content exceeding 50% was achieved in the treated biomass, with cellulose and lignin identified as the main remaining constituents in the solid fraction. This approach represents a sustainable and efficient pathway for the valorisation of agri-food residues through green chemistry, supporting the advancement of integrated biorefineries and fostering the transition towards circular bioeconomy models. Trabajo presentado en: XVI International Scientific Agriculture Symposium "Agrosym 2025", Jahorina, Bosnia and Herzegovina, October 2-5, 2025 Wed, 01 Jan 2025 00:00:00 GMT https://hdl.handle.net/10259/12220 2025-01-01T00:00:00Z https://hdl.handle.net/10259/12219 Sustainable production of lactic acid from corn stover using catalytic hydrothermal treatments: a comparative study of alkaline and Lewis acid catalysis Candela Gil, Helena; Illera Gigante, Alba Ester; Barea Gómez, Pedro; Beltrán Calvo, Sagrario; Sanz Díez, Mª Teresa Corn stover, an abundant lignocellulosic agricultural residue, offers great potential as a feedstock for the sustainable production of high value-added biochemicals, contributing to circular economy strategies and rural development. Among these compounds is lactic acid (LA), a key monomer in the synthesis of polylactic acid (PLA)—an environmentally friendly alternative to petroleumbased plastics due to its biodegradable properties and low environmental impact. PLA is suitable for food packaging and agricultural plastic applications. This study explores two sustainable approaches for second-generation lactic acid production from corn stover (5% w/v) using hydrothermal treatments assisted by catalysts: Ca(OH)₂ for alkaline catalysis and AlCl₃ for Lewis acid catalysis. In the first process, Ca(OH)₂ at 0.3 M achieves a 32% yield (12.4 g/L LA) under isothermal conditions at 260 °C. An excess of catalyst is required to maintain an optimal OH⁻/sugar monomer molar ratio of 2.61. In contrast, in the second process, AlCl₃ at 0.016 M produces a 20.7% yield (7.4 g/L LA) at 190 °C. However, higher AlCl₃ concentrations promote the degradation of dehydration products into levulinic and formic acids, decreasing LA selectivity. Alkaline catalysis required higher temperatures for optimal yield, while Lewis acid catalysis was more temperature-sensitive, as prolonged exposure leads to LA degradation. Both Ca(OH)₂ and AlCl₃ are promising catalysts due to their low cost, availability, and low toxicity, making them viable for converting corn residues into lactic acid in a sustainable biorefinery context. Trabajo presentado en: XVI International Scientific Agriculture Symposium "Agrosym 2025", Jahorina, Bosnia and Herzegovina, October 2-5, 2025 Wed, 01 Jan 2025 00:00:00 GMT https://hdl.handle.net/10259/12219 2025-01-01T00:00:00Z https://hdl.handle.net/10259/12218 One-pot lactic acid production using subcritical water as a sustainable approach in the valorization of corn stover Illera Gigante, Alba Ester; Candela Gil, Helena; Barea Gómez, Pedro; Beltrán Calvo, Sagrario; Sanz Díez, Mª Teresa Corn stover is an agricultural waste obtained after the corn grain harvest, formed by the stalks, leaves and cobs of the plant. Its production worldwide accounts with more than 1 billion tons per year, and it is usually considered as feed for livestock. However, due to its interesting composition of cellulose and hemicellulose fractions, corn stover can be considered as a valuable biomass for the production of biofuels or value-added chemicals. Among the different possibilities, the production of lactic acid was chosen due to its broad application in the food and chemical industries, as a food preservative or flavoring, or as a precursor of polylactic acid, respectively. In this regard, a one-pot subcritical water treatment was proposed for the production of lactic acid from corn stover. Under subcritical conditions, water ionic product increases to a great extent, acquiring Brønsted acid properties, which combined with the Lewis acidity provided by the lanthanide Yb3+, makes a synergistic effect and favors the lactic acid production route from the pentoses and hexoses present in the biomass. The effect of temperature was tested from 180 to 260 °C. It was determined that a minimum temperature of 220 °C was required to successfully hydrolyze the cellulose and hemicellulose fractions into convertible monosaccharides. This temperature was selected as the optimum one, which yielded a 22 % lactic acid yield after just one hour, and showed a low HMF production, showing the high selectivity of the process at this temperature. One-pot subcritical water treatment of corn stover proved to be a sustainable solution for the valorization of the agricultural waste. Trabajo presentado en: XVI International Scientific Agriculture Symposium "Agrosym 2025", Jahorina, Bosnia and Herzegovina, October 2-5, 2025 Wed, 01 Jan 2025 00:00:00 GMT https://hdl.handle.net/10259/12218 2025-01-01T00:00:00Z