Effective valorisation of distillery stillage by integrated production of lactic acid and high quality feed

Advances on the Valorisation and Functionalization of By-Products and Wastes from Cereal-Based Processing Industry

Cereals have been one of the major food resources for human diets and animal feed for thousands of years, and a large quantity of by-products is generated throughout the entire processing food chain, from farm to fork. These by-products mostly consist of the germ and outer layers (bran) derived from dry and wet milling of the grains, of the brewers' spent grain generated in the brewing industry, or comprise other types obtained from the breadmaking and starch production industries. Cereal processing by-products are an excellent low-cost source of various compounds such as dietary fibres, proteins, carbohydrates and sugars, minerals and antioxidants (such as polyphenols and vitamins), among others. Often, they are downgraded and end up as waste or, in the best case, are used as animal feed or fertilizers. With the increase in world population coupled with the growing awareness about environmental sustainability and healthy life-styles and well-being, the interest of the industry and the global market to provide novel, sustainable and innovative solutions for the management of cereal-based by-products is also growing rapidly. In that respect, these promising materials can be valorised by applying various biotechnological techniques, thus leading to numerous economic and environmental advantages as well as important opportunities towards new product development (NPD) in the food and feed industry and other types such as chemical, packaging, nutraceutical (dietary supplements and food additives), cosmetic and pharmaceutical industries. This review aims at giving a scientific overview of the potential and the latest advances on the valorisation of cereal-based by-products and wastes. We intended it to be a reference document for scientists, technicians and all those chasing new research topics and opportunities to explore cereal-based by-products through a circular economy approach.

Multi-Product Lactic Acid Bacteria Fermentations: A Review

Industrial biotechnology is a continuously expanding field focused on the application of microorganisms to produce chemicals using renewable sources as substrates. Currently, an increasing interest in new versatile processes, able to utilize a variety of substrates to obtain diverse products, can be observed. A robust microbial strain is critical in the creation of such processes. Lactic acid bacteria (LAB) are used to produce a wide variety of chemicals with high commercial interest. Lactic acid (LA) is the most predominant industrial product obtained from LAB fermentations, and its production is forecasted to rise as the result of the increasing demand of polylactic acid. Hence, the creation of new ways to revalorize LA production processes is of high interest and could further enhance its economic value. Therefore, this review explores some co-products of LA fermentations, derived from LAB, with special focus on bacteriocins, lipoteichoic acid, and probiotics. Finally, a multi-product process involving LA and the other compounds of interest is proposed.

Non-thermal plasma and ultrasound-assisted open lactic acid fermentation of distillery stillage

Stillage is the main by-product of bioethanol production and the cost of its treatment significantly affects the economy of bioethanol production. A process of thermal sterilization before lactic acid fermentation (LAF) is energy demanding and is causing deterioration of valuable compounds in stillage. In this study, ultrasound (UT) and plasma (PT) treatments were used for microbial inactivation, and a significant reduction in the number of viable microorganisms in the stillage after PT and UT was observed. After application of treatment, LAF by Lactobacillus rhamnosus ATCC 7469 was initiated. The concentration of LA is used to quantify the efficiency of the stillage revalorization. The highest LA productivity of 1.21 g/Lh and yield of 0.82 g/g were obtained after PT, while UT of 10 min provided productivity of 1.02 g/Lh and LA yield of 0.69 g/g. The results were benchmarked against closed LAF. Around 20% better revalorization of stillage by PT was achieved when compared with conventional sterilization. In addition, an excellent L (+) LA stereoselectivity of 95.5% was attained after PT. From the aspect of energy efficiency, that of PT was three times lower than UT and almost ten times lower than thermal sterilization, but it is the most expensive due to the high consumption of gas which could reduce application of closed Ar atmosphere on larger scales. This way, a simpler and energy efficient process for LA production on stillage was accomplished by "open" fermentation.

Effect of Fermented Medicinal Plants as Dietary Additives on Food Preference and Fecal Microbial Quality in Dogs

Simple Summary

Dog foods are becoming more equivalent to human foods, and functional additives are being included in their diets to promote health. In this study, turmeric, glasswort, and Ganghwa mugwort were used as medicinal plants and were subjected to fermentation by autochthonous Enterococcus faecium. Fermentation significantly improved the in vitro antioxidant activities of these plants. Food preference tests of dog foods containing these fermented medicinal plants were conducted in beagles.

Abstract

This research determined the antioxidant activities of medicinal plants fermented by Enterococcus faecium and their subsequent applications as dog food additives. Turmeric (5%, w/v), glasswort (2.5%, w/v), Ganghwa mugwort (2.5%, w/v), and their mixture (5%, w/v) were fermented by autochthonous E. faecium (1%, v/v) for 72 h. Bacterial cell counts and pH were monitored during fermentation. Total polyphenol content (TPC), total flavonoid content (TFC), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and intracellular superoxide scavenging activity in bovine mammary alveolar epithelial (MAC-T) cells were measured with the fermented and non-fermented samples. Only the antioxidant capacity of the mixture was increased after fermentation. However, intracellular superoxide level in MAC-T cells was significantly reduced after treatment with fermented plant samples (p < 0.001) as compared with that in non-fermented plants. Fermented plants were then sprayed at 1% (v/w) onto dog foods. TPC, TFC, ABTS radical scavenging activity, and DPPH radical scavenging activity of dog foods were significantly enhanced after the addition of fermented plants. Food preference testing was conducted using a two-pan method—control diet vs. four treatment diets—for 4 days for each additive diet, a total 16 days in 9 beagles. Feces were collected to enumerate bacterial counts. Preferences for glasswort and Ganghwa mugwort were higher than those of the control (p < 0.05). Furthermore, fecal microbiota enumeration displayed a higher number of beneficial microorganisms in treated groups. These results suggest that fermented plants with enhanced antioxidant abilities might be useful as potential additives for dog foods.

Utilization of brewing and malting by-products as carrier and raw materials in l-(+)-lactic acid production and feed application

Application of agro-industrial by-products for the production of lactic acid was studied in this paper. Brewer's spent grain (BSG), malt rootlets (MR), brewer's yeast (BY), and soy lecithin (SL) were used as raw materials in L-(+)-LA fermentation by free and immobilized Lactobacillus rhamnosus ATCC 7469. The BSG, solid remains after BSG and MR hydrolysis (BSGMRSR), and MR were evaluated as carriers for batch and repeated batch fermentations with immobilized cells. During batch fermentations with immobilized cells, high cell viability (10 to 11 log CFU/g) was achieved on all carriers. In batch fermentation with BSG as a carrier, the highest LA yield of 93.79% and volumetric productivity of 1.15 g/L/h were obtained. Furthermore, very high LA yield (95.46%), volumetric productivity (1.98 g/L/h) and L. rhamnosus viability (11.5 log CFU/g) were achieved in repeated batch fermentations with the cells immobilized on this carrier. The immobilized cells showed high survival rate (94-95%) during exposure to simulated gut condition. Based on the analysis of BSGMRSR, and BY solid remains, and on in vitro evaluation of the probiotic characteristics of immobilized cells, it was observed that they could satisfy the recommendations for high-quality feed preparation.

Possibility of L-(+)-lactic acid fermentation using malting, brewing, and oil production by-products

Industrial by-products such as brewer's spent grain (BSG) hydrolysate, malt rootlets extract (MRE) and soybean meal extract (SME) were used for L-(+) lactic acid (LA) production by a pure L. rhamnosus ATCC 7469 strain. The effect of the addition of MRE (10-50%) or SME (10-50%) in BSG hydrolysate on batch and fed-batch LA fermentation was evaluated. The addition of MRE and SME increased the concentration of free amino nitrogen (FAN) and essential minerals (Fe, Mg, Mn, and Zn), which had a positive effect on the fermentation. Also, the MRE addition significantly lowered C/N ration to a more favorable level for the efficient LA fermentation. In batch fermentation, the highest LA concentration (25.73 g/L), yield (86.31%), and volumetric productivity (0.95 g/L h^-1), were obtained with the addition of 50% MRE. Further increase in LA concentration to 58.01 g/L, yield to 88.54%, and volumetric productivity to 1.19 g/L h^-1 was achieved in fed-batch fermentation with addition of 50% MRE. A high optical purity of LA with 99.7% of L-(+)-isomer was obtained on the substrate based on industrial by-products. In addition, solid remains after BSG hydrolysis and MRE and SME preparation, together with the biomass of L. rhamnosus separated after the fermentation could be a good base for feed preparation.

Wastes from bioethanol and beer productions as substrates for l(+) lactic acid production - A comparative study

Waste substrates from bioethanol and beer productions are cheap, abundant and renewable substrates for biorefinery production of lactic acid (LA) and variability in their chemical composition presents a challenge in their valorisation. Three types of waste substrates, wasted bread and wasted potato stillage from bioethanol production and brewers' spent grain hydrolysate from beer production were studied as substrates for the production of l(+) LA and probiotic biomass by Lactobacillus rhamnosus ATCC 7469. The correlation of the content of free alpha amino nitrogen and the production of LA was determined as a critical characteristic of the waste media for efficient LA production by L. rhamnosus on the substrates which contained equal amount of fermentable sugars. A maximal LA productivity of 1.54gL(-1)h(-1) was obtained on wasted bread stillage media, whilst maximal productivities achieved on the potato stillage and brewers' spent grain hydrolysate media were 1.28gL(-1)h(-1)and 0.48gL(-1)h(-1), respectively. A highest LA yield of 0.91gg(-1) was achieved on wasted bread stillage media, followed by the yield of 0.81gg(-1) on wasted potato stillage and 0.34gg(-1) on brewers' spent grain hydrolysate media. The kinetics of sugar consumption in the two stillage substrates were similar while the sugar conversion in brewers' spent grain hydrolysate was slower and less efficient due to significantly lower content of free alpha amino nitrogen. The lignocellulosic hydrolysate from beer production required additional supplementation with nitrogen.