Brewers' spent grain (BSG) is the most abundant by-product generated in the beer-brewing process. This material consists of the barley grain husks obtained as solid residue after the production of wort. BSG is rich in fibre and protein and, to date, the main use for the elimination of this by-product has been as an animal feed. However, because of its nutritional content, BSG is of interest for application and fortification of human food products, particularly in view of its low cost and availability in large amounts. In addition, the importance of BSG as an ingredient and potential source of health-promoting bioactive components is beginning to be recognised. The investigation of alternative uses of BSG is pertinent, not only from the perspective of the brewer who can benefit from valorisation of this by-product, but also from an environmental perspective as the recycling and re-use of industrial wastes and by-products has become increasingly important. This review presents the current knowledge on BSG, covering its production, composition and methods for the release of valuable components, and focuses on the potential health benefits attributed to its constituents and the use of this brewer by-product in food applications. Copyright © 2016 The Institute of Brewing & Distilling

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jib.363

Brewers' spent grain: a review with an emphasis on food and health

Most developing nations continuously produce abundant agro-industrial residues such as brewer’s spent grain (BSG), which are underexploited. BSG as the main by-product of brewing industry, representing  approximately 85% of total by-products generated, is rich in cellulose and non-cellulosic polysaccharides and has a strong potential to be recycled. Due to the global intense pressure towards green environmental  technology, both academic and industrial researchers are putting more efforts to reduce the amount of such wastes by finding alternative uses apart from the current general use as an animal feed. Thus, several products are increasingly being sought from BSG. This article intends to review some of the products that can be realized from BSG and also to stimulate researchers to explore further, especially in developing new value-added products. Key words : Brewer’s spent grain, polysaccharide, animal feed, residue.

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Brewer’s spent grain: A review of its potentials and applications

Work on glomalin-related soil protein produced by arbuscular mycorrhizal (AM) fungi (AMF) has been limited because of the unknown identity of the protein. A protein band cross-reactive with the glomalin-specific antibody MAb32B11 from the AM fungus Glomus intraradices was partially sequenced using tandem liquid chromatography-mass spectrometry. A 17 amino acid sequence showing similarity to heat shock protein 60 (hsp 60) was obtained. Based on degenerate PCR, a full-length cDNA of 1773 bp length encoding the hsp 60 gene was isolated from a G. intraradices cDNA library. The ORF was predicted to encode a protein of 590 amino acids. The protein sequence had three N-terminal glycosylation sites and a string of GGM motifs at the C-terminal end. The GiHsp 60 ORF had three introns of 67, 76 and 131 bp length. The GiHsp 60 was expressed using an in vitro translation system, and the protein was purified using the 6xHis-tag system. A dot-blot assay on the purified protein showed that it was highly cross-reactive with the glomalin-specific antibody MAb32B11. The present work provides the first evidence for the identity of the glomalin protein in the model AMF G. intraradices, thus facilitating further characterization of this protein, which is of great interest in soil ecology.

The arbuscular mycorrhizal fungal protein glomalin is a putative homolog of heat shock protein 60

This chapter describes the use of different plant and vegetable food residues as nutraceuticals and functional foods. Different nutraceuticals are mentioned and explained. Their uses are well addressed along with their disease management and their action as nutraceutical delivery vehicles.

https://www.mdpi.com/2304-8158/5/4/88/pdf

Plant Food Residues as a Source of Nutraceuticals and Functional Foods

Lactobacillus sake can use arginine via the arginine deiminase (ADI) pathway. We designed degenerate primers based on an alignment of known sequences of ornithine transcarbamoylase (OTC)-encoding genes in order to amplify the L. sake counterpart sequences by PCR. Screening a genomic library of L. sake in lambdaEMBL3 allowed us to isolate a clone containing a 10-kb L. sake genomic DNA insert. Sequence analysis revealed that the genes involved in arginine catabolism were clustered and encoded ADI (arcA), OTC (arcB), carbamate kinase (arcC), and a putative carrier with high similarity to the arginine/ornithine antiporter of Pseudomonas aeruginosa (arcD). Additionally, a putative transaminase-encoding gene (arcT) was located in this region. The genes followed the order arcA arcB arcC arcT arcD, which differs from that found in other microorganisms. arcA, arcB, arcC, and arcD mutants were constructed, and the ADI pathway was impaired in all of them. Transcriptional studies indicated that arcA gene is subject to catabolite repression, and under the conditions used, several transcripts could be detected, suggesting the existence of different initiation sites or processing of a larger mRNA.

Structural and functional analysis of the gene cluster encoding the enzymes of the arginine deiminase pathway of Lactobacillus sake.

Brewers' spent grain (BSG) is a readily available, high volume low cost byproduct of brewing and is a potentially valuable resource for industrial exploitation. The variation in BSG composition and the implications for microbiological spoilage by a resident microflora might affect the potential to use BSG as a reliable food-grade industrial feedstock for value-added downstream processing. Fresh samples of BSG from a range of 10 breweries have been analysed for their microbial and chemical composition. The results show that a resident microflora of mainly thermophilic aerobic bacteria ( 7  g -1 fresh weight) persists on BSG. This population is susceptible to rapid change but at the point of production BSG can be considered microbiologically stable. Chemically, BSG is rich in polysaccharides, protein and lignin. Residual starch can contribute up to 13% of the dry weight and BSG from lager malts has higher protein content than that from ale. In general, at the point of production, BSG is a relatively uniform chemical feedstock available for industrial upgrading. Differences between breweries should not present problems when considering BSG for industrial exploitation but susceptibility to microbial colonisation is identified as a potential problem area which might restrict its successful exploitation.

Profiling brewers' spent grain for composition and microbial ecology at the site of production

A method for the direct screening of bacterial λ libraries by polymerase chain reaction technology has been developed. This technique permits the identification and isolation of specific DNA sequences without the need for any filter hybridisation or radioactive probing. This strategy has been used to isolate a gene encoding lactate dehydrogenase from a Lactococcus lactis λ library.

Rapid isolation of genes from bacterial lambda libraries by direct polymerase chain reaction screening

The composition of brewers' spent grain (BSG) makes it susceptible to microbial attack and chemical deterioration. This can constrain its appeal as an industrial feedstock. The current study has monitored the effects of BSG storage as fresh material (20 degrees C), refrigerated and autoclaved, measured against frozen material in relation to microbial proliferation and modification to plant cell wall polysaccharides and component phenolic acids. At 20 degrees C there was a rapid colonization by microbes and an associated loss of components from BSG. Refrigeration gave a similar but lower level response. When stored frozen, BSG showed no changes in composition but autoclaving resulted in a solubilization of polysaccharides and associated phenolics. Changes were associated with the temperature profile determined during autoclaving and were also partially due to the breakdown of residual starch. Losses of highly branched arabinoxylan (AX) and the related decrease in ferulic acid cross-linking were also found. The results confirm the need for storage stabilization of BSG and demonstrate that the methods selected for stabilization can themselves lead to a substantial modification to BSG.

Kerry J.A. I'Anson

Papers

Profiling brewers' spent grain for composition and microbial ecology at the site of production

Rapid isolation of genes from bacterial lambda libraries by direct polymerase chain reaction screening

Effect of Storage Conditions on the Microbial Ecology and Biochemical Stability of Cell Wall Components in Brewers’ Spent Grain