Wet fractionation process to produce high protein and high fiber products from brewer's spent grain

Food Waste from Campus Dining Hall as a Potential Feedstock for 2,3-Butanediol Production via Non-Sterilized Fermentation

Food waste is a major issue that is increasingly affecting our environment. More than one-third of food is wasted, resulting in over $400 billion in losses to the U.S. economy. While composting and other small recycling practices are encouraged from person-to-person, it is not enough to balance the net loss of 80 million tons per year. Currently, one of the most promising routes for reducing food waste is through microbial fermentation, which can convert the waste into valuable bioproducts. Among the compounds produced from fermentation, 2,3-butanediol (2,3-BDO) has gained interest recently due to its molecular structure as a building block for many other derivatives used in perfumes, synthetic rubber, fumigants, antifreeze agents, fuel additives, and pharmaceuticals. Waste feedstocks, such as food waste, are a potential source of renewable energy due to their lack of cost and availability. Food waste also possesses microbial requirements for growth such as carbohydrates, proteins, fats, and more. However, food waste is highly inconsistent and the variability in composition may hinder its ability to be a stable source for bioproducts such as 2,3-BDO. This current study focuses specifically on post-consumer food waste and how 2,3-BDO can be produced through a non-model organism, Bacillus licheniformis YNP5-TSU during non-sterile fermentation. From the dining hall at Tennessee State University, 13 food waste samples were collected over a 6-month period and the compositional analysis was performed. On average, these samples consisted of fat (19.7%), protein (18.7%), ash (4.8%), fiber (3.4%), starch (27.1%), and soluble sugars (20.9%) on a dry basis with an average moisture content of 34.7%. Food waste samples were also assessed for their potential production of 2,3-BDO during non-sterile thermophilic fermentation, resulting in a max titer of 12.12 g/L and a 33% g/g yield of 2,3-BDO/carbohydrates. These findings are promising and can lead to the better understanding of food waste as a defined feedstock for 2,3-BDO and other fermentation end-products.

Sequential Extraction and Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy Monitoring in the Biorefining of Brewer's Spent Grain

The brewing industry plays a significant role in producing a substantial annual volume of by-products, which contributes to the global accumulation of food waste. The primary by-product generated is brewer's spent grain (BSG), a lignocellulosic biomass rich in proteins, fiber, and moisture content. Leveraging biorefining and valorization techniques for BSG represents a promising strategy to enhance sustainability, resilience, and circularity within the brewing chain. To date, most studies have focused on extracting proteins from BSG. Yet, it is crucial to note that the fiber part of BSG also holds considerable potential for biorefining processes. This study introduces a novel sequential extraction method designed to integrally recover the major components of BSG. Notably, it introduces a reactive extraction approach that enables the simultaneous extraction and tuneable functionalization of the hemicellulose component. Additionally, the study assesses the utility of the attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy as a user-friendly tool to monitor and evaluate the effectiveness of the fractionation process. This spectroscopic technique can provide valuable insights into the changes and composition of BSG throughout the extraction process.

Protein recovery from brewery solid wastes

Brewing produces significant amounts of solid waste during the process: spent cereals (BSG), hops and spent yeast (BSY). These residues are sustainable sources of valuable nutrients and functional compounds like proteins, polyphenols, and polysaccharides. This review describes the three solid wastes and the different extraction techniques for protein recovery. The protein obtained can be used as a new source of non-animal protein or as a functional and bioactive ingredient. Particular attention was given to methods using conventional technologies (alkaline and ethanolic extraction) and more innovative approaches (enzymes, microwaves, ultrasound, pressurized liquids and sub-critical water extraction). Although the BSG is used in some industrial applications, studies in operating conditions, cost, energy efficiency, and product performance are still required to consolidate these solid wastes as a source of non-animal protein. The application of proteins is also an important question when choosing the extraction method.

Extraction, Composition, Functionality, and Utilization of Brewer’s Spent Grain Protein in Food Formulations

In recent years, brewer’s spent grain (BSG) has gained attention as a plant-based protein source because it occurs in large quantities as a by-product of beer brewing. BSG can contribute to future food requirements and support the development of a circular economy. In light of the dynamic developments in this area, this review aims to understand the proteins present in BSG, and the effect of extraction techniques and conditions on the composition, physicochemical, and techno-functional properties of the obtained protein extracts. The water-insoluble hordeins and glutelins form the major protein fractions in BSG. Depending on the beer brewing process, the extraction technique, and conditions, the BSG protein isolates predominantly contain B, C, and ϒ hordeins, and exhibit a broad molecular weight distribution ranging between <5 kDa and >250 kDa. While the BSG isolates obtained through chemical extraction methods seem promising to obtain gelled food products, physical and enzymatic modifications of BSG proteins through ultrasound and proteolytic hydrolysis offer an effective way to produce soluble and functional protein isolates with good emulsifying and foaming capabilities. Specifically tailored protein extracts to suit different applications can thus be obtained from BSG, highlighting that it is a highly valuable protein source.

Foaming properties are improved by interactions between brewer's spent grain proteins and carrageenans in aqueous solution

BACKGROUND

Foaming properties and macromolecular interactions in solution among brewer's spent grain proteins (CP) and iota and lambda carrageenans (i-CG and l-CG, respectively) as a function of aqueous medium pH (2-6) and protein-polysaccharide ratio, R_CP:CG (1:1, 2:1 and 4:1), were studied. At these conditions, the CP colloidal stability was favored by the formation of soluble electrostatic complexes with CG. Fluorescence (intrinsic and extrinsic) spectroscopy and dynamic light scattering techniques, including particle size and ζ-potential analysis, were applied to know the phase behavior of the biopolymer systems. The bubbling method was used to produce foams, and the foam expansion (%) and half-life time (t_1/2 ) were determined.

RESULTS

Both CG promoted an increased Trp fluorescence emission depending on the pH, suggesting conformational changes in CP. The CG in mixed systems produced a significant decrease in the extrinsic fluorescence intensity, mainly at low pH values, highlighting a reduction in CP surface hydrophobicity. At the examined pH range, the ζ-potential values for mixed-systems were negative, and their magnitudes were intermediate between CP and CG, revealing the associative electrostatic nature of biopolymer interactions, which were dependent on the R_CP:CG . The particle size analysis confirmed the formation of soluble electrostatic complexes in solution. Finally, using i-CG at pH 2 or 3 and 2:1 R_CP:CG , the best foaming properties for mixed systems were observed.

CONCLUSION

The formation of electrostatic complexes with a compact assembly among biopolymers, high negative net charge, and colloidal stability convert the CP-CG mixed solutions into promising biopolymer systems for food foams production. © 2022 Society of Chemical Industry.

Emerging challenges for the agro-industrial food waste utilization: A review on food waste biorefinery

Modernization and industrialization has undoubtedly revolutionized the food and agro-industrial sector leading to the drastic increase in their productivity and marketing thereby accelerating the amount of agro-industrial food waste generated. In the past few decades the potential of these agro-industrial food waste to serve as bio refineries for the extraction of commercially viable products like organic acids, biochemical and biofuels was largely discussed and explored over the conventional method of disposing in landfills. The sustainable development of such strategies largely depends on understanding the techno economic challenges and planning for future strategies to overcome these hurdles. This review work presents a comprehensive outlook on the complex nature of agro-industrial food waste and pretreatment methods for their valorization into commercially viable products along with the challenges in the commercialization of food waste bio refineries that need critical attention to popularize the concept of circular bio economy.

An Update Regarding the Bioactive Compound of Cereal By-Products: Health Benefits and Potential Applications

Cereal processing generates around 12.9% of all food waste globally. Wheat bran, wheat germ, rice bran, rice germ, corn germ, corn bran, barley bran, and brewery spent grain are just a few examples of wastes that may be exploited to recover bioactive compounds. As a result, a long-term strategy for developing novel food products and ingredients is encouraged. High-value compounds like proteins, essential amino acids, essential fatty acids, ferulic acid, and other phenols, tocopherols, or β-glucans are found in cereal by-products. This review aims to provide a critical and comprehensive overview of current knowledge regarding the bioactive compounds recovered from cereal by-products, emphasizing their functional values and potential human health benefits.

Towards a Complete Exploitation of Brewers’ Spent Grain from a Circular Economy Perspective

In the present work, brewers’ spent grain (BSG), which represents the major by-product of the brewing industry, was recovered from a regional brewery and fractionated in order to obtain a complete valorization. In particular, the whole process was divided in two main parts. A first pretreatment with hot water in an autoclave allowed the separation of a solution containing the soluble proteins and sugars, which accounted for 25% of the total starting biomass. This first step allowed the preparation of a medium that was successfully employed as a valuable growing medium for different microbial fermentations, leading to valuable fungal biomass as well as triglycerides with a high content of linear or branched fatty acids, depending on the microorganism used. The solid water-insoluble residue was then submitted to a lignocellulose deep eutectic solvent-mediated fractionation, which allowed the recovery of two important main fractions: BSG cellulose and BSG lignin. The latter product was tested as potential precursor for the development of cement water reducers with encouraging results. This combination of treatments of the waste biomass appeared to be a promising sustainable strategy for the development of the full exploitation of BSG from a circular economy perspective.

A New Method to Overcome Carboxyamide Formation During AFEX Pretreatment of Lignocellulosic Biomass

Lignin-carbohydrate complexes (LCCs) in the plant cell wall are responsible for providing resistance against biomass-degrading enzymes produced by microorganisms. Four major types of lignin-carbohydrate bonds are reported in the literature, namely, benzyl ethers, benzyl esters, phenyl glycosides, and acetyl ester linkages. Ester’s linkages in the plant cell wall are labile to alkaline pretreatments, such as ammonia fiber expansion (AFEX), which uses liquid or gaseous ammonia to cleave those linkages in the plant cell wall and reduce biomass recalcitrance. Two competing reactions, notably hydrolysis and ammonolysis, take place during AFEX pretreatment process, producing different aliphatic and aromatic acids, as well as their amide counterparts. AFEX pretreated grasses and agricultural residues are known to increase conversion of biomass to sugars by four- to five-fold when subjected to commercial enzyme hydrolysis, yielding a sustainable feedstock for producing biofuels, biomaterials, and animal feed. Animal feed trials on dairy cows have demonstrated a 27% increase in milk production when compared to a control feedstock. However, the presence of carboxamides in feedstocks could promote neurotoxicity in animals if consumed beyond a certain concentration. Thus, there is the need to overcome regulatory hurdles associated with commercializing AFEX pretreated biomass as animal feed in the United States. This manuscript demonstrates a modified pretreatment for increasing the digestibility of industrial byproducts such as Brewer’s spent grains (BSG) and high-fiber meal (HFM) produced from BSG and dry distillers grains with soluble (DDGS), while avoiding the production of carboxamides. The three industrial byproducts were first treated with calculated amounts of alkali such as NaOH, Ca(OH)2, or KOH followed by AFEX pretreatment. We found that 4% alkali was able to de-esterify BSG and DDGS more efficiently than using 2% alkali at both 10 and 20% solids loading. AFEX pretreatment of de-esterified BSG, HFM, and DDGS produced twofold higher glucan conversion than respective untreated biomass. This new discovery can help overcome potential regulatory issues associated with the presence of carboxamides in ammonia-pretreated animal feeds and is expected to benefit several farmers around the world.

Starch and protein recovery from brewer's spent grain using hydrothermal pretreatment and their conversion to edible filamentous fungi - A brewery biorefinery concept

This study aimed at recovering a highly concentrated starch and protein stream from the brewer's spent grain (BSG). The effect of pretreatment temperature and retention time on the solubilization of starch and protein; and the generation of fermentation inhibitors were studied. Then, the application of recovered streams for fungal cultivation was evaluated using different edible fungi Aspergillus oryzae, Neurospora intermedia, and Rhizopus delemar. The hydrothermal pretreatment resulted in the highest solubilized starch concentration, 43 g/L, corresponding to 83% solubilization of initial BSG starch content. The highest protein concentration was 27 g/L (48% solubilization of initial BSG protein content). Cultivation with Neurospora intermedia on the recovered streams from the two best pretreatment conditions, 140 ℃ for 4 h and 180 ℃ for 30 min, resulted in pure fungal biomass with the highest protein content 59.62% and 50.42% w/w, respectively. Finally, a brewery biorefinery was proposed for the valorization of BSG.

Brewers' spent grain in food systems: Processing and final products quality as a function of fiber modification treatment

The nutritional properties of brewers' spent grain (BSG) have been widely studied, considering its potential as a healthy food ingredient. Because of its fiber composition (amount and ratio), however, adding BSG into the food matrix to bring about changes in physical properties has been believed to impact negatively on the acceptability of the final products' properties, particularly color and texture. Fiber modification can enhance the quality of fiber and can be applied to BSG. Although it appears challenging, modifying fiber composition requires further study, particularly if the acceptability of the final products is to be improved. Furthermore, the level of fiber degradation during the modification treatment needs to be examined to meet the increased demand for BSG in final food products. This concise synthesis provides a new perspective for increasing the use of BSG as a food ingredient that is characterized by high nutrition and acceptability.

Optimised Fractionation of Brewer’s Spent Grain for a Biorefinery Producing Sugars, Oligosaccharides, and Bioethanol

Brewer’s spent grain (BSG) is the main by-product of the beer brewing process. It has a huge potential as a feedstock for bio-based manufacturing processes to produce high-value bio-products, biofuels, and platform chemicals. For the valorisation of BSG in a biorefinery process, efficient fractionation and bio-conversion processes are required. The aim of our study was to develop a novel fractionation of BSG for the production of arabinose, arabino-xylooligomers, xylose, and bioethanol. A fractionation process including two-step acidic and enzymatic hydrolysis steps was investigated and optimised by a response surface methodology and a desirability function approach to fractionate the carbohydrate content of BSG. In the first acidic hydrolysis, high arabinose yield (76%) was achieved under the optimised conditions (90 °C, 1.85 w/w% sulphuric acid, 19.5 min) and an arabinose- and arabino-xylooligomer-rich supernatant was obtained. In the second acidic hydrolysis, the remaining xylan was solubilised (90% xylose yield) resulting in a xylose-rich hydrolysate. The last, enzymatic hydrolysis step resulted in a glucose-rich supernatant (46 g/L) under optimised conditions (15 w/w% solids loading, 0.04 g/g enzyme dosage). The glucose-rich fraction was successfully used for bioethanol production (72% ethanol yield by commercial baker’s yeast). The developed and optimised process offers an efficient way for the value-added utilisation of BSG. Based on the validated models, the amounts of the produced sugars, the composition of the sugar streams and solubilised oligo-saccharides are predictable and variable by changing the reaction conditions of the process.

Chemical Compositions of Edamame Genotypes Grown in Different Locations in the US

The consumption of edamame [Glycine max (L.) Merr.] in the US has rapidly increased due to its nutritional value and potential health benefits. In this study, 10 edamame genotypes were planted in duplicates in three different locations in the US—Whitethorne, Virginia (VA), Little Rock, Arkansas (AR), and Painter, VA. Edamame samples were harvested at the R6 stage of the bean development when beans filled 80–90% of the pod cavity. Afterward, comprehensive chemical composition analysis, including sugars, alanine, protein, oil, neutral detergent fiber (NDF), starch, ash, and moisture contents, were conducted on powdered samples using standard methods and the total sweetness was calculated based on the measured sugars and alanine contents. Significant effects of the location were observed on all chemical constituents of edamame (p &lt; 0.05). The average performance of the genotypes was higher in Whitethorne for the contents of free sucrose (59.29 mg/g), fructose (11.42 mg/g), glucose (5.38 mg/g), raffinose (5.32 mg/g), stachyose (2.34 mg/g), total sweetness (78.63 mg/g), and starch (15.14%) when compared to Little Rock and Painter. The highest soluble alanine (2.67 mg/g), NDF (9.00%), ash (5.60%), and moisture (70.36%) contents were found on edamame planted in Little Rock while edamame planted in Painter had the highest crude protein (43.11%) and oil (20.33%) contents. Significant effects of genotype were observed on most of the chemical constituents (p &lt; 0.05) except NDF and raffinose. Among the 10 genotypes, R13-5029 consistently had high sucrose content and total sweetness across the three locations, meanwhile it had relatively high protein and fiber contents. Overall, the results indicate that to breed better edamame genotypes in the US, both genotype and planting location should be taken into considerations.

Physical, structural and antioxidant properties of brewer's spent grain protein films

BACKGROUND

The development of brewer's spent grain protein (BSG-PC) films with potential active packaging properties was investigated. Films were prepared by casting protein dispersions at different pH values (2, 8, 11), plasticizers [polyethylene glycol (PEG) or glycerol] and levels (0-0.25 g g^-1 ) of PEG. Mechanical, water-barrier and solubility, optical, antioxidant (reducing power, ABTS^•+ and lipidic radical scavenging), and antimicrobial properties of films were determined. Also, the structural characteristics of films were evaluated by attenuated total reflectance-Fourier transform infrared spectroscopy.

RESULTS

Only films prepared at pH 2 and plasticized by PEG were homogeneous in appearance and could be manipulated; thus, different levels of PEG were studied at this pH. Higher PEG concentrations increased water solubility, water vapor permeability and elongation at break, and decreased tensile strength and elastic modulus. PEG increased α-helix structure only when 0.10 g PEG g-1 BSG-PC was used. This could be related to the better mechanical properties of F_0.10 films (higher tensile strength, and elastic modulus) with respect to the other films. Antioxidant activity depended on PEG concentration, whereas no antimicrobial properties against Bacillus cereus, Salmonella newport and Penicillium corylophylum were detected.

CONCLUSION

The formulations with 0.10 and 0.15 g PEG g^-1 BSG-PC appear to be the most promising, balancing mechanical, water-barrier properties and the antioxidant capacity of these films. Moreover, BSG proteins could be a cheap alternative for the preparation of biodegradable films, which are capable of being used as active food packaging. © 2020 Society of Chemical Industry.

The role of microorganisms on biotransformation of brewers' spent grain

Brewers' spent grain (BSG) is the most abundant by-product of brewing. Due to its microbiological instability and high perishability, fresh BSG is currently disposed of as low-cost cattle feed. However, BSG is an appealing source of nutrients to obtain products with high added value through microbial-based transformation. As such, BSG could become a potential source of income for the brewery itself. While recent studies have covered the relevance of BSG chemical composition in detail, this review aims to underline the importance of microorganisms from the stabilization/contamination of fresh BSG to its biotechnological exploitation. Indeed, the evaluation of BSG-associated microorganisms, which include yeast, fungi, and bacteria, can allow their safe use and the best methods for their exploitation. This bibliographical examination is particularly focused on the role of microorganisms in BSG exploitation to (1) produce enzymes and metabolites of industrial interest, (2) supplement human and animal diets, and (3) improve soil fertility. Emerging safety issues in the use of BSG as a food and feed additive is also considered, particularly considering the presence of mycotoxins.Key points• Microorganisms are used to enhance brewers' spent grain nutritional value.• Knowledge of brewers' spent grain microbiota allows the reduction of health risks. Graphical abstract.

Brewer’s Spent Grains: Possibilities of Valorization, a Review

This review was based on updated research on how to use brewer’s spent grains (BSG). The use of BSG was considered both in food, as an ingredient or using value-added components derived from brewer’s spent grain, or in non-food products such as pharmaceuticals, cosmetics, construction, or food packaging. BSG is a valuable source of individual components due to its high nutritional value and low cost that is worth exploiting more to reduce food waste but also to improve human health and the environment. From the bioeconomy point of view, biological resources are transformed into bioenergetically viable and economically valuable products. The pretreatment stage of BSG biomass plays an important role in the efficiency of the extraction process and the yield obtained. The pretreatments presented in this review are both conventional and modern extraction methods, such as solvent extractions or microwave-assisted extractions, ultrasonic-assisted extractions, etc.