Effect of protein during hydrothermal carbonization of brewer's spent grain

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.

Recycling of Brewer's Spent Grain as a Biosorbent by Nitro-Oxidation for Uranyl Ion Removal from Wastewater

Developing biosorbents derived from agro-industrial biomass is considered as an economic and sustainable method for dealing with uranium-contaminated wastewater. The present study explores the feasibility of oxidizing a representative protein-rich biomass, brewer's spent grain (BSG), to an effective and reusable uranyl ion adsorbent to reduce the cost and waste generation during water treatment. The unique composition of BSG favors the oxidation process and yields in a high carboxyl group content (1.3 mmol/g) of the biosorbent. This makes BSG a cheap, sustainable, and suitable raw material independent from pre-treatment. The oxidized brewer's spent grain (OBSG) presents a high adsorption capacity of U(VI) of 297.3 mg/g (c 0(U) = 900 mg/L, pH = 4.7) and fast adsorption kinetics (1 h) compared with other biosorbents reported in the literature. Infrared spectra (Fourier transform infrared), 13C solid-state nuclear magnetic resonance spectra, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis were employed to characterize the biosorbents and reveal the adsorption mechanisms. The desorption and reusability of OBSG were tested for five cycles, resulting in a remaining adsorption of U(VI) of 100.3 mg/g and a desorption ratio of 89%. This study offers a viable and sustainable approach to convert agro-industrial waste into effective and reusable biosorbents for uranium removal from wastewater.

Subcritical water as hydrolytic medium to recover and fractionate the protein fraction and phenolic compounds from craft brewer's spent grain

The valorization of the brewer's spent grain (BSG) generated in a craft beer industry was studied by subcritical water hydrolysis in a semi-continuous fixed-bed reactor. Temperature was varied from 125 to 185 °C at a constant flow rate of 4 mL/min. Biomass hydrolysis yielded a maximum of 78% of solubilized protein at 185 °C. Free amino acids presented a maximum level at 160 °C with a value of 55 mg free amino acids/g_protein-BSG. Polar amino acid presented a maximum at lower temperatures than non-polar amino acids. The maximum in total phenolic compounds was reached at 185 °C. This maximum is the same for aldehyde phenolic compounds such as vanillin, syringic and protocatechuic aldehyde; however, for hydroxycinnamic acids, such as ferulic acid and p-coumaric, the maximum was obtained at 160 °C. This allows a fractionation of the bioactive compounds. Subcritical water addresses opportunities for small breweries to be incorporated within the biorefinery concept.

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.

Nitrogen-Containing Hydrochar: The Influence of Nitrogen-Containing Compounds on the Hydrochar Formation

Hydrothermal carbonization (HTC) of fructose and urea containing solutions was conducted at 180 °C to study the influence of nitrogen-containing compounds on conversion and product properties. The concentration of fructose was fixed, while the concentration of urea was gradually increased to study its influence on the formation of nitrogen-containing hydrochar (N-HC). The degradation of urea has an important influence on the HTC of fructose. The Maillard reaction (MR) promotes the formation of N-HC in acidic conditions. However, in alkaline conditions, MR promotes the formation of bio-oil at the expense of N-HC. Alkaline conditions reduce N-HC yield by catalyzing fragmentation reactions of fructose and by promoting the isomerization of fructose to glucose. The results showed that adjusting the concentration of nitrogen-containing compounds or the pH value of the reaction environment is important to force the reaction toward the formation of N-HC or N-bio-oil.

Activated hydrochar produced from brewer's spent grain and its application in the removal of acetaminophen

Acetaminophen has shown a gradual increase in detection in surface waters. Although present in low concentrations, it should be removed to prevent deleterious effects. Thus, adsorption onto activated carbon is emphasized. Adsorbents may be produced by hydrothermal carbonization (HTC), an environmental-friendly process. Therefore, this work aimed to investigate the use of HTC, verifying its application in acetaminophen removal. Brewer's spent grain (BSG), its hydrochar (HC-BSG) and its activated hydrochar (AHC-BSG) were characterized. HTC provided material with high carbon content. Lignocellulosic breakdown has been demonstrated in HC-BSG and AHC-BSG, but in the latter it was more intense as a result of activation with KOH. Also, a high surface area was found in AHC-BSG (1512.83 m² g^-1), resulting in an adsorption of 318.00 mg g^-1. The pseudo-second-order and Langmuir models were fitted to the experimental data. Therefore, HTC was effective as a pretreatment for AHC-BSG, resulting in significant acetaminophen removals.

Innovation and strategic orientations for the development of advanced biorefineries

Advanced biorefineries, which aim at valorizing biomass (from agriculture, forestry, aquaculture, among others) into a wide spectrum of products and bioenergy, are seen today as key to implement a sustainable biobased economy. Although different concepts of biorefinery are currently under development, further research and improvement are still required to obtain environmentally friendly and economically feasible commercial scale biorefineries. Valorization of all biomass components and integration of different disciplines are some of the strategies that have been considered to improve the economic and environmental performance. This paper summarizes and discusses the most recent innovations and strategic orientations for the development of advanced biorefineries. Focus is given on the valorization of non-carbohydrate components of biomass (protein, acetic acid and lignin), on-site and tailor-made production of enzymes, big data analytics, and interdisciplinary efforts. The idea is to provide new insights and directions to support the development and large-scale implementation of biorefineries.

Towards the Properties of Different Biomass-Derived Proteins via Various Extraction Methods

This study selected three representative protein-rich biomass-brewer's spent grain (BSG), pasture grass (PG), and cyanobacteria (Arthrospira platensis; AP) for protein extraction with different extraction methods (alkaline treatment, aqueous extraction, and subcritical water extraction). The yield, purity, molecular weight, oil-water interfacial tension, and thermal stability of the obtained proteins derived from different biomass and extraction methods were comprehensively characterized and compared. In the view of protein yield and purity, alkaline treatment was found optimal for BSG (21.4 and 60.2 wt.%, respectively) and AP (55.5 and 68.8 wt.%, respectively). With the decreased oil-water interfacial tension, the proteins from all biomass showed the potential to be emulsifier. BSG and AP protein obtained with chemical treatment presented excellent thermal stability. As a novel method, subcritical water extraction is promising in recovering protein from all three biomass with the comparable yield and purity as alkaline treatment. Furthermore, the hydrolyzed protein with lower molecular weight by subcritical water could promote its functions of foaming and emulsifying.

Mild hydrothermally treated brewer's spent grain for efficient removal of uranyl and rare earth metal ions

The increasing concerns on uranium and rare earth metal ion pollution in the environment require sustainable strategies to remove them from wastewater. The present study reports an eco-friendly approach to convert a kind of protein-rich biomass, brewer's spent grain (BSG), into effective biosorbents for uranyl and rare earth metal ions. The employed method reduces the energy consumption by performing the hydrothermal treatment at a significantly lower temperature (150 °C) than conventional hydrothermal carbonization. In addition, with the aid of the Maillard reaction between carbohydrates and proteins forming melanoidins, further activation processes are not required. Treatment at 150 °C for 16 h results in an altered biosorbent (ABSG) with increased content of carboxyl groups (1.46 mmol g⁻¹) and a maximum adsorption capacity for La³⁺, Eu³⁺, Yb³⁺ (pH = 5.7) and UO₂²⁺ (pH = 4.7) of 38, 68, 46 and 221 mg g⁻¹, respectively. Various characterization methods such as FT-IR, ¹³C CP/MAS NMR, SEM-EDX and STA-GC-MS analysis were performed to characterize the obtained material and to disclose the adsorption mechanisms. Aside from oxygen-containing functional groups, nitrogen-containing functional groups also contribute to the adsorption. These results strongly indicate that mild hydrothermal treatment of BSG could be applied as a greener, low-cost method to produce effective adsorbents for uranyl and rare earth metal ion removal.

Effective biosorbent ABSG is obtained via hydrothermal treatment of BSG at low temperature without activation, minimizing energy consumption and environmental impact.