More than just a beer—the potential applications of by-products from beer manufacturing in polymer technology

Beer is the most popular alcoholic beverage in the world, and its popularity is continuously growing. Currently, global beer production is estimated at around 2 billion hectoliters. Nevertheless, the increasing production capacity implicates the rising issue of generated by-products—brewers’ spent grain, spent hops, spent yeast, and wastewater. They are generated in massive amounts, so having in mind the current pro-ecological trends, it is crucial to look for their utilization methods. Among the possibilities, particular attention should be drawn to polymer technology. This sector can efficiently use different lignocellulosic materials, which could be applied as fillers for polymer composites or sources of particular chemical compounds. Moreover, due to their chemical composition, brewing industry by-products may be used as functional fillers and additives. They could be introduced to enhance the materials’ resistance to oxidation, microbes, or fungi. These issues should be considered especially important in the case of biodegradable polymers, whose popularity is growing over the last years. This paper summarizes the literature reports related to the composition and potential applications of the brewing industry by-products in polymer technology. Moreover, potential directions of research based on the possibilities offered by the brewing industry by-products are presented.

Brewing By-Products as a Source of Natural Antioxidants for Food Preservation

Brewer’s spent grain (BSG) and brewer’s spent hops (BSH) are the major solid by-products of the brewing industry. The present work evaluated their potential as an alternative source of natural antioxidants. The efficacy of different solvents (MilliQ water, 0.75% NaOH, 50% MeOH, 50% MeOH + 0.3% HCl and 50% Acetone) for extracting polyphenols of these by-products was firstly evaluated, with NaOH showing the best results. The extraction conditions were optimized using the response surface methodology, and were determined to be 1.45% NaOH and 80 °C. BSG extracts showed the highest total polyphenol content (24.84–38.83 µmol GAE/g), whereas the BSH showed the lowest value (24.84 ± 1.55 µmol GAE/g). In general, BSG extracts presented significantly higher antioxidant capacity (ABTS, ORAC). Ferulic acid was the main polyphenol in all BSG extracts (156.55–290.88 mg/100 g), whereas in BSH, this compound was not detected. The addition of 10% BSG extract in o/w emulsions (stored 14 days) showed a reduction in the formation of primary oxidation products of 97%. In the emulsions covered with polylactic acid active films (1% BSG), this reduction corresponded to 35%. Hence, this study demonstrates the potential of these by-products as natural antioxidant sources for protecting food systems against oxidation.

The Application Potential of Hop Sediments from Beer Production for Composting

The chemical composition of hop sediments from beer brewing and fermentation gives them the potential for further use. These wastes are not generated in large amounts, but the absence of proper characteristics may lead to processing errors. This study examines the possibility of using hop waste for aerobic biological transformation processes (composting). The study was carried out on two hop sediments from two different technological stages of beer production: hot trub and spent hops. Chemical, microbiological, and biochemical analyses were performed in the composted hop sediments, as was the assessment of phytotoxicity to Lepidium sativum L. The tested feedstocks were partially inhabited by microorganisms and thus safe from an epidemiological point of view, and they were not a source of microbial contamination. Inhibitory properties for plant development were found for hot trub, which most likely result from the organic compound content. If it is only a small portion of its biomass, the mineral composition of hot trub does not exclude the possibility of its composting. Spent hops were characterized by a significant total nitrogen content, which affected the composting process. Composting this sediment required the selection of substrates with a widely C:N ratio.

By-Products in the Malting and Brewing Industries—Re-Usage Possibilities

Beer production includes the formation of different by-products such as wastewater, spent grains, spent hops, and yeast. In addition to these well-known by-products, it is necessary to mention germ/rootlets, which also remain after the malting process. Given that a huge amount of beer is produced annually worldwide, by-products are available in large quantities throughout the year. Spent grains, spent hops, and spent yeasts are high-energy raw materials that possess a great potential for application in the branch of biotechnology, and the food industry, but these by-products are commonly used as livestock feed, disposed of in the fields, or incinerated. Breweries by-products can be utilized for microalgae production, biofuel production, extraction of proteins, polyphenolic, antioxidative substances, etc. This paper aims to address each of these by-products with an emphasis on their possible application in biotechnology and other industries.

Wpływ ekstraktu z wychmielin (Humulus lupulus L.) na przeżywalność ludzkich nowotworowych i prawidłowych komórek jelita

Introduction. The hop (Humulus lupulus L.) is used in the production of beer and is responsible for its taste and specific aroma. The female cones of this plant as well as the spent hops after the hops extraction by supercritical CO2 are the source of the substances with high biological activity. These include phenolic compounds among others: catechin, epicatechin, quercetin, kaempferol having a lot of properties which could be used in the medicine. They also demonstrate anti-proliferative activity which is responsible for the inhibition of the cancer cells growth. Aim. The aim of the present study was to evaluate the effect of spent hops extract on the viability of cancer and normal colon epithelial cells. Materials and methods. Three cell lines were tested: two colon cancer lines (SW-480 and HT-29) and normal epithelial colon (CCD841CoN) cell line. The activity of the spent hops extract was tested on the basis of cell growth by means of the MTT test. The cells were incubated with the tested extract at 37°C with the constant of CO2 content in atmosphere for 24, 48, 72 hours. Results. The results showed that tested extract inhibited the growth of two colon cancer cell lines (SW-480 and HT-29) more than the growth of normal cell line (CCD841CoN). The IC50 value for SW-480 cell line was obtained at the concentration 400 μg/ml after 48-hours incubation, for HT-29 cell line at the concentration 200 μg/ml after 72-hours incubation while for normal epithelial CCD841CoN cell line the IC50 value was not received. Conclusions. The spent hops extract has anti-proliferative activity. The most susceptible to extract was SW-480 cell line. The normal CCD841CoN epithelial cells were the least sensitive to the extract activity.

Antimicrobial Properties of Spent Hops Extracts, Flavonoids Isolated Therefrom, and Their Derivatives

Hop cones preparations possess a wide range of biological activities including antimicrobial properties. In this work, we evaluated the effect of various organic extracts obtained from spent hops, as well as six hops flavonoids and their twenty natural and synthetic derivatives on human and plant microbial pathogens. Methylene chloride, acetone, ethyl acetate, and methanol were used as extractants. Seven flavonoids, among them two natural (α,β-dihydroxanthohumol and 8-prenylnaringenin) showed significant activity against methicillin sensitive and resistant Staphylococcus aureus and Staphylococcus epidermidis strains with the lowest MIC80 value of 0.5 µg/mL. The crude ethyl acetate, acetone, and methanol extracts from the spent hops exhibited antifungal activity against Fusarium oxysporum, F. culmorum, and F. semitectum with the lowest MIC50 of 0.5 mg/mL, while the methylene chloride extract exerted antifungal activity against Botrytis cinerea with the MIC50 of 1 mg/mL. The preparation obtained after the removal of xanthohumol from the spent hops crude extracts retained up to 95% of activity. These findings suggest that various spent hops extracts may be effective agents for the control of plant pathogens of economic importance, like Botrytis cinerea and Fusarium oxysporum, while some compounds from spent hops or their derivatives may become useful for staphylococcal infections.

Antifeedant activity of xanthohumol and supercritical carbon dioxide extract of spent hops against stored product pests

Xanthohumol, a prenylated flavonoid from hops, and a supercritical carbon dioxide extract of spent hops were studied for their antifeedant activity against stored product insect pests: Sitophilus granarius L., Tribolium confusum Duv. and Trogoderma granarium Everts. Xanthohumol exhibited medium deterrent activity against the adults of S. granarius L. and larvae of T. confusum Duv. The spent hops extract was more active than xanthohumol towards the adults of T. confusum Duv. The potential application of the crude spent hops extract as a feeding deterrent against the stored product pests is proposed.