Recovery and reuse of ionic liquid cholinium glycinate in the treatment of brewery spent grain

Recently, the ability of the biocompatible ionic liquid cholinium glycinate (N1112OHGly) for waste vegetable delignification like brewery spent grain (BSG) has been proved. However, the technical viability should march hand in hand with economic competitiveness. Therefore, the first step must address the reuse of the ionic liquid to mitigate the high cost associated with the synthesis of this kind of neoteric solvents. Different antisolvent-based strategies have been considered, in the present research work, to produce a delignified carbohydrate rich material (CRM) and reuse the ionic liquid. It was checked that the addition of a mixture of water: acetone (1:1 v/v) was able to efficiently precipitate carbohydrates with high levels of delignification, while about 97% of the ionic liquid is recovered at a purity near 72%. The use of this strategy allowed reusing N1112OHGly for 5 cycles and FTIR and XRD spectroscopy, scan electron microscopy (SEM) and, quantitative acid hydrolysis evidenced the suitability of the proposed process for the competitive sequential BSG delignification. Liquid chromatography sheds light on the recovery percentages and purity of the ionic liquid after each use.Xunta de Galicia | Ref. ED481A-2017/320Xunta de Galicia | Ref. ED431B 2018/5

Enzymatic hydrolysis of brewer’s spent grain to obtain fermentable sugars

Lignocellulosic biomass is a feedstock with the potential to be converted into value-added bioproducts. The use of enzymatic hydrolysis allows the cleavage of lignocellulose into their monomeric units, but there are some drawbacks that make its use in industrial biocatalysis unfeasible. In the present study, we describe the hydrolysis of brewer’s spent grain (BSG) with an enzymatic cocktail produced by Aspergillus niger CECT 2700 and its comparison with commercial enzymes. In addition, it was determined whether pretreating the BSG (non-pressurized alkaline hydrolysis or treatment with cholinium glycinate ionic liquid) is necessary. Results show that both pretreatments enhanced xylose release (10.55±0.07g/L and 8.14±0.13g/L respectively), meanwhile the hydrolysis of raw BSG with the enzymatic cocktail produced solutions containing high levels of glucose (18.45±1.66g/L) and xylose (6.38±0.26g/L).Ministerio de Economía y Competitividad | Ref. CTQ2015-71436-C2-1-

Biorefining brewery spent grain polysaccharides through biotuning of ionic liquids

Brewery spent grain (BSG), a relevant waste from beer industry mainly composed of polysaccharides and lignin, is experiencing a surge in the production with its associated environmental impact. Thus, this manuscript bets in the application of aqueous solutions of a cholinium-based ionic liquid (IL) containing glycinate as anion ([N1112OH][Gly]) for an efficient delignification pretreatment. The operation at 90 °C yielded drastic lignin reduction (75.89%), greater than the levels attained when a traditional imidazolium-based IL (1-ethyl-3-methylimidazolium acetate, [C2C1im][C1COO]), was used (40.18%). The advantages of this pretreatment positively impacted the subsequent saccharification reaction, as the levels were increased up to about 1.5 times regarding the control (no IL) or the imidazolium-based pretreatment. ATR-FTIR spectrometry and scanning electron microscopy turned out to be useful tools to monitor the structural changes exerted. The results presented in this work make up the basis for a rational design of bio-ILs for delignification of lignocellulosic materials.Xunta de Galicia | Ref. ED431F 2016/007Ministerio de Economía y Competitividad | Ref. CTQ2015-71436-C2-1-

Valorization of chestnut (Castanea sativa) residues: characterization of different materials and optimization of the acid-hydrolysis of chestnut burrs for the elaboration of culture broths

Four kinds of waste from the industrial processing of chestnuts (Castanea sativa), namely leaves, pruned material and burrs from chestnut tree plus chestnut shells, were characterized to determine their content in polymers and thus their potential use in biorefinery processes. Results revealed that chestnut burrs have the highest polysaccharide content being the most promising for carrying out the subsequent stages of acid hydrolysis. Treatment with diluted sulfuric acid (prehydrolysis) allowed the solubilization of xylose, glucose and arabinose, but also some toxic compounds such as furan derivatives, aliphatic acids and phenolic constituents. Xylose, the main component released in the hemicellulosic hydrolyzates, was maximized by using a 3**(2–0) full factorial design combined with desirability function. At optimum conditions set at 130 °C and 3% (w/v) H 2 SO 4 , this value was 22.6 g L −1 xylose. Three concentrations of activated charcoal (1, 2.5 and 5% w/v) were evaluated to remove certain unwanted byproducts, and it was found that under the highest dosage, 95.27 ± 0.03% of the color was removed with an almost total reduction of furan derivatives, making this liquor an appropriate basis for the development of suitable culture media for lactic acid bacteria. To validate this hypothesis three lactic acid bacteria, namely Lactobacillus plantarum, Lactobacillus pentosus and Lactococcus lactis were positively tested finding lactic acid yields of 0.89, 0.92 and 0.83 g/L·h respectively.Axencia Galega de Innovació

Biorefinery of brewery spent grain to obtain bioproducts with high value-added in the market

The brewery industry is under economic and environmental pressure to minimize residual management costs, particularly brewery spent grain (BSG), which accounts for 80–85% (w/w) of the total by-products generated. BSG is a lignocellulosic material primarily composed of carbohydrates, proteins and lipids. Developing a biorefinery model for conversion of BSG into value-added products is a plausible idea. Previous work optimized the pretreatment of BSG with the ionic liquid [N1112OH][Gly] and further release of fermentable sugar-containing solutions by enzymatic hydrolysis, using an enzymatic cocktail obtained by solid-state fermentation of BSG with Aspergillus brasiliensis CECT 2700 and Trichoderma reesei CECT 2414. The current work ends the biorefinery process, studying the fermentation of these culture media with two LAB strains, Lactobacillus pentosus CECT 4023 and Lactobacillus plantarum CECT 221, from which the production of organic acids, bacteriocins, and microbial biosurfactants (mBS) was obtained. In addition to the bacteriocin activity observed, a mass balance of the whole biorefinery process quantified the production of 106.4 g lactic acid and 6.76 g mBS with L. plantarum and 116.1 g lactic acid and 4.65 g mBS with L. pentosus from 1 kg of dry BSG. Thus, BSG shows a great potential for waste valorization, playing a major role in the implementation of biomass biorefineries in circular bioeconomy.Agencia Estatal de Investigación | Ref. PID2020–115879RB-I00São Paulo Research Foundation | Ref. 2018/25511–1São Paulo Research Foundation | Ref. 2023/09256–0Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil) | Ref. 408783/2021–4Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil) | Ref. 312923/2020–1Xunta de Galicia | Ref. GPC-ED431B 2021/23Universidade de Vigo/CISU