Lactic acid fermentation of brewer's spent grain hydrolysate by Lactobacillus rhamnosus with yeast extract addition and pH control

Lactic acid (LA) is a versatile chemical with a wide range of applications in food, pharmaceutical, cosmetic, textile and polymer industries. Brewer's spent grain (BSG) is the most abundant brewing by‐product. In this study BSG hydrolysates were used for LA fermentation by Lactobacillus rhamnosus ATCC 7469. The aim of this study was to evaluate the effects of pH control during fermentation, reducing sugar content and yeast extract content in BSG hydrolysate on LA fermentation parameters. The pH control greatly increased reducing sugar utilization, l ‐(+)‐LA content, yield and volumetric productivity. The highest l ‐(+)‐LA yield and volumetric productivity were achieved with the reducing sugar content of 54 g/L. Yeast extract addition significantly increased reducing sugar utilization, l ‐(+)‐LA content, L. rhamnosus cell viability, l ‐(+)‐LA yield and volumetric productivity. The highest l ‐(+)‐LA content (39.38 g/L), L. rhamnosus cell viability (9.67 log CFU/mL), l ‐(+)‐LA yield (91.29%) and volumetric productivity (1.69 g/L/h) were achieved with the reducing sugar content of 54 g/L and yeast extract content of 50 g/L. Copyright © 2017 The Institute of Brewing & Distilling     

Brewers' spent grain and thin stillage as raw materials in l‐(+)‐lactic acid fermentation

Brewer's spent grain (BSG) hydrolysates were used for l ‐(+)‐lactic acid (LA) fermentation by Lactobacillus rhamnosus ATCC 7469. In this study the effect of the addition of various amounts of thin stillage (TS) in BSG hydrolysate on LA fermentation parameters were evaluated. TS addition significantly increased utilization of glucose by up to 43.0%. In batch fermentation the highest LA concentration and volumetric productivity of 31.0 g/L, and 0.93 g/L/h, respectively, were obtained with the addition of 50% TS. L. rhamnosus cell viability also increased with the addition of 50% TS (by 2.4%). TS addition significantly increased free amino nitrogen concentration (by up to 209%) which is important for bacterial growth. A strong positive correlation between free amino nitrogen and LA concentration was noted. Compared with the results obtained in the batch fermentation (50% TS), significantly higher LA concentration, yield and volumetric productivity (54.8, 1.9 and 4.0%, respectively) were achieved in fed‐batch fermentation with glucose and TS addition. The results suggest that the combination of the by‐products of brewing and bioethanol industries could be suitable for LA production. Copyright © 2017 The Institute of Brewing & Distilling     

Fed‐batch l‐(+)‐lactic acid fermentation of brewer's spent grain hydrolysate

Brewer's spent grain (BSG) hydrolysates were used for l ‐(+)‐lactic acid (LA) fermentation by Lactobacillus rhamnosus ATCC 7469. The aim of this study was to evaluate fed‐batch LA fermentation of BSG hydrolysate with the addition of glucose, glucose and yeast extract, and wort during LA fermentation and its effect on fermentation parameters such as LA concentration, its volumetric productivity and yield, and L. rhamnosus cell viability. The highest LA yield, volumetric productivity and concentration of 93.3%, 2.0 g/L/h, and 116.1 g/L, respectively, were achieved with glucose and yeast extract addition during fermentation. In fed‐batch fermentation with glucose and yeast extract addition significantly higher LA concentration, yield and volumetric productivity (by 194.8; 2.2, and 20.7%, respectively) were achieved compared with batch fermentation. The results indicated that fed‐batch fermentation could be used to increase LA fermentation efficiency. Copyright © 2017 The Institute of Brewing & Distilling     

The influence of calcium-carbonate and yeast extract addition on lactic acid fermentation of brewer's spent grain hydrolysate

Brewer's spent grain (BSG) is the major by-product of the brewing industry, representing around 85% of the total by-products generated. In this study BSG hydrolysate was produced using optimal conditions. Hydrolysates were used for lactic acid (LA) fermentation by Lactobacillus fermentum (PL-1) and Lactobacillus rhamnosus (ATCC 7469). The aim of this study was to evaluate possibilities of the BSG hydrolysate utilization as a substrate for LA fermentation. The effect of calcium-carbonate (2%) and yeast extract (0.5 to 5%) addition in hydrolysate on LA fermentation were investigated. The LA production by L. fermentum and L. rhamnosus in BSG hydrolysate was influenced by calcium-carbonate and yeast extract supplementation. L. fermentum produced a racemic mixture of L-(+)- and D-(−)-LA while L. rhamnosus produced mostly L-(+)-LA (95–98%) in all fermentations. Calcium-carbonate addition increased total LA yield by 13% in L. fermentum fermentations and by 17% in L. rhamnosus fermentations. Yeast extract addition increased total LA yield by 4–26% in L. fermentum fermentations and by 6–8% in L. rhamnosus fermentations.     

Bioconversion of agro‐industrial by‐products to lactic acid using Lactobacillus sakei and two Pediococcus spp. strains

The aim of this study was to evaluate the bioconversion efficiency of rich in cellulose agro‐industrial by‐products such as wheat bran (WB), spent distiller's grain with solids (DGS), brewer's spent grain (BSG) and lupin (Lupinus angustifolius L.) wholemeal fraction (LF) to lactic acid (LA) using acid tolerant lactic acid bacteria (LAB) strains Lactobacillus sakei KTU05‐06, Pediococcus acidilactici KTU05‐7 and P. pentosaceus KTU05‐9. Carbohydrase preparation Depol^? 692L was used for the hydrolysis of non‐starch polysaccharides. Analysed raw materials were suitable substrates for LAB propagation and L‐lactic acid production. The lowest pH (3.6) was found in LF medium after 48 h fermentation with P. acidilactici and P. pentosaceus strains. The lowest pH (3.86) was measured in WB fermented with L. sakei, and in DGS and BSG (pH 3.8 and 3.9 respectively) fermented with P. acidilactici. The highest endoxylanase activity was excreted by the P. acidilactici and P. pentosaceus (84 and 69 XU g^?1 respectively), and the highest α‐amylase activity was of L. sakei (255.6 AU g^?1) after 24 h incubation in WB medium. The L‐lactic acid concentration of 86.11 g kg^?1 was reached after the bioconversion of hydrolysed WB in combination with 48 h fermentation by P. pentosaceus KTU05‐9 strain. LA contents between 222 and 282 mg kg^?1 was produced from lupin processing residues via fermentation using P. acidilactici and P. pentosaceus KTU05‐9 strains. The major challenge within the presented study is the viability of tested LAB in cereal waste media and effective LA production at a low pH (3.6–3.8).     

Application of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry as a monitoring tool for in‐house brewer's yeast contamination: a proof of concept

Contamination of brewer's pitching yeast cultures with wild‐type yeasts or bacteria is unwanted as it can corrupt the fermentation outcome and causes huge economic losses for the brewing industry. The applicability of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) as a fast tool to monitor the purity of brewer's yeast cultures was investigated. This proof of concept was examined for a brewer's yeast strain contaminated with wild‐type yeast and for bottled beer produced by fermentation with that particular contaminated brewer's yeast strain. The data demonstrated that MALDI‐TOF MS is very suitable to discriminate between brewing and non‐brewing yeast strains. Copyright © 2014 The Institute of Brewing & Distilling     

Acid hydrolysis and fermentation of brewer's spent grain to produce xylitol

The hemicellulosic fraction of brewer's spent grain (BSG) was hydrolysed with diluted acid under different conditions of liquid/solid ratio (8–12 g g⁻¹), sulfuric acid concentration (100–140 mg g⁻¹ dry matter) and reaction time (17–37 min) in order to produce a liquor with a large amount of xylose and good fermentability to produce xylitol. Results showed that all the evaluated reaction conditions were able to hydrolyse xylan and arabinan with efficiencies higher than 85.8 and 95.7% respectively, and even under the mildest reaction condition a considerable amount (92.7%) of the hemicellulosic fraction could be extracted. The hydrolysates presented different fermentabilities when used as fermentation media for xylitol production by Candida guilliermondii yeast, owing to the differences in their composition. Based on statistical analysis, the best condition for BSG acid hydrolysis was the use of a liquid/solid ratio of 8 g g⁻¹, 100 mg H₂SO₄ g⁻¹ dry matter and a reaction time of 17 min. Under this condition a high extraction efficiency of hemicellulosic sugars (92.7%) and good fermentation results (Y_P/S = 0.70 g g⁻¹ and Q_P = 0.45 g dm⁻³ h⁻¹) were attained. Copyright © 2005 Society of Chemical Industry     

Antioxidant capacity,arabinoxylans content and in vitro glycaemic index of cereal-based snacks incorporated with brewer's spent grain

Extruded snacks and breadsticks were formulated with increasing levels of brewer's spent grain (BSG). The phenolic content increased by 4 and 7 fold with BSG addition in extrudates (40 g/100 g) and in breadsticks (35 g/100 g), respectively. Consequently, antioxidant capacity (DPPH, FRAP) also increased despite a recorded loss of phenolic compounds in extruded snacks. Arabinoxylans content increased up to 20 and 25 g of BSG addition/100 g of formulated extruded snacks and breadsticks, respectively. Further addition of BSG did not improve the content of arabinoxylans due to the possible formation of polysaccharide–protein complexes. Medium GI breadsticks were obtained with 35 g of BSG incorporation/100 g formulation. Phenolic content, arabinoxylans content and antioxidant capacity increased in the final products with BSG addition while the glycaemic response decreased. BSG can be incorporated as an ingredient in the formulation of extruded snacks and breadsticks generating products richer in antioxidants and fibre and with low GI.     

Effects of wheat gluten hydrolysates fractionated by different methods on the growth and fermentation performances of brewer's yeast under high gravity fermentation

Wheat gluten hydrolysates (WGH) were fractionated through ultrafiltration membrane with molecular weight (Mw) cut‐off of 3 kDa and ethanol precipitation, respectively. WGH and their fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast under high gravity fermentation. Results showed that WGH and their fractions exhibited significant differences in biomass accumulation, viability, ethanol yield, free amino nitrogen and sugar consumptions under high gravity fermentation. Compared to WGH, the fractions with Mw < 3 kDa and the supernatant of WGH treated with ethanol precipitation showed better fermentation performance for brewer's yeast. The relatively lower molecular weight and the higher levels of Leu, Lys, His and Arg in these two fractions might be responsible for their bioactivity for brewer's yeast. Thus, both ultrafiltration and ethanol precipitation could be used as efficient methods for enriching peptides with significant growth‐ and fermentation‐promoting activity for brewer's yeast under high gravity fermentation.     

Effects of soy protein hydrolysates on the growth and fermentation performances of brewer's yeast

Soy protein isolate was hydrolysed with Alcalase, Papain, Flavorzyme and Protemax, respectively, and further fractioned by ultrafiltration. The resulting soy protein hydrolysates (SPH) and their ultrafiltration fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast. Results showed that degree of hydrolysis, molecular weight distribution and amino acid composition of SPH significantly affected the growth, viability and fermentation performance of brewer's yeast. The SPH prepared from different proteolytic enzymes exhibited distinct growth‐ and fermentation‐promoting activity for brewer's yeast. The SPH treated with Protemax for 9 h and with the molecular weight below 3 kDa showed the highest growth‐promoting activity and induced more rapidly reducing sugar consumption and higher ethanol production. The relatively lower molecular weight and the hydrophilic and electropositive amino acid residues (Lys, His, Arg and Ile) in SPH might be responsible for its functionality, promoting the growth and fermentation of brewer's yeast.     

Improvement of L(+)‐lactic acid production from cassava wastewater by Lactobacillus rhamnosus B 103

BACKGROUND: L (+)‐Lactic acid is used in the pharmaceutical, textile and food industries as well as in the synthesis of biodegradable plastics. The aim of this study was to investigate the effects of different medium components added in cassava wastewater for the production of L (+)‐lactic acid by Lactobacillus rhamnosus B 103. RESULTS: The use of cassava wastewater (50 g L^?1 of reducing sugar) with Tween 80 and corn steep liquor, at concentrations (v/v) of 1.27 mL L^?1 and 65.4 mL L^?1 respectively led to a lactic acid concentration of 41.65 g L^?1 after 48 h of fermentation. The maximum lactic acid concentration produced in the reactor after 36 h of fermentation was 39.00 g L^?1 using the same medium, but the pH was controlled by addition of 10 mol L^?1 NaOH. CONCLUSION: The use of cassava wastewater for cultivation of L. rhamnosus is feasible, with a considerable production of lactic acid. Furthermore, it is an innovative proposal, as no references were found in the scientific literature on the use of this substrate for lactic acid production. Copyright © 2010 Society of Chemical Industry     

Impact of buffering capacity on the acidification of wort by brewing‐relevant lactic acid bacteria

Acidified wort produced biologically using lactic acid bacteria (LAB) has application during sour beer production and in breweries adhering to the German purity law (Reinheitsgebot ). LAB cultures, however, suffer from end product inhibition and low pH, leading to inefficient lactic acid (LA) yields. Three brewing‐relevant LAB (Pediococcus acidilactici AB39, Lactobacillus amylovorus FST2.11 and Lactobacillus plantarum FST1.7) were examined during batch fermentation of wort possessing increasing buffering capacities (BC). Bacterial growth was progressively impaired when exposed to higher LA concentrations, ceasing in the pH range of 2.9–3.4. The proteolytic rest (50°C) during mashing was found to be a major factor improving the BC of wort. Both a longer mashing profile and the addition of an external protease increased the BC (1.21 and 1.24, respectively) compared with a control wort (1.18), and a positive, linear correlation (R ² = 0.957) between free amino nitrogen and BC was established. Higher levels of BC led to significant greater LA concentration (up to +24%) after 48 h of fermentation, reaching a maximal value of 11.3 g/L. Even higher LA (maximum 12.8 g/L) could be obtained when external buffers were added to wort, while depletion of micronutrient(s) (monosaccharides, amino acids and/or other unidentified compounds) was suggested as the cause of LAB growth cessation. Overall, a significant improvement in LA production during batch fermentation of wort is possible when BC is improved through mashing and/or inclusion of additives (protease and/or external buffers), with further potential for optimization when strain‐dependent nutritional requirements, e.g. sugar and amino acids, are considered. Copyright © 2017 The Institute of Brewing & Distilling     

Impact of the Long‐Term Maintenance Method of Brewer's Yeast on Fermentation Course,Yeast Vitality and Beer Characteristics

The effect of the long‐term maintenance method used with a brewer's yeast on its technological properties was determined in laboratory fermentation trials with a 12°P all‐malt wort. The trials were performed at a constant temperature and under conditions of constant substrate concentration. Two cultures of a bottom fermenting yeast, Saccharomyces pastorianus RIBM 95, were tested — one culture was maintained by subculturing on wort agar slopes at 4°C and the other culture underwent a three year storage in liquid nitrogen at minus 196°C. Parameters under investigation included yeast vitality measured as acidification power (AP), fermentation time needed to reach an alcohol level of 4%, the yeast cell count, sedimentation of the yeast during the fermentation, and the production of beer flavour compounds in green beer. The yeast culture stored for three years in liquid nitrogen displayed a higher count of suspended cells, required a shorter time to attenuate the wort to produce 4% alcohol and produced a 1.5 to 2.5‐fold higher concentration of a number of flavour compounds. The long‐term storage method did not affect the sedimentation ability and vitality of the yeast strain tested.     

Isolation and partial purification of mannose-specific agglutinin from brewer's yeast involved in flocculation

Yeast cell-agglutinating activity, designated agglutinin (possible lectin), was isolated from cell walls of both non-flocculent and flocculent brewer's yeast cells. Agglutinin-mediated aggregation of yeast cells in a manner similar to flocculation with respect to specific mannose-sensitivity, pH-dependence and calcium-dependence. Agglutinating activity was found to be heat-stable and protease-insensitive. Furthermore, addition of agglutinin to flocculent cells strongly stimulated the flocculation ability of the cells, whereas addition to non-flocculent cells rendered these cells weakly flocculent. Agglutinin was found to be released from flocculent cells during the course of a flocculation assay, but not from non-flocculent cells. Presence of mannose during the assay inhibited release of agglutinin. Our results suggest that (i) mannose-specific agglutinin is continuously synthesized during growth of brewer's yeast cells, (ii) agglutinin is present in cell walls of non-flocculent cells but is unable to bind its ligand on other cells, and (iii) the ability of yeast cells to flocculate in a flocculation assay depends, among other factors, on release of agglutinin from the cells. A 10-kDa polypeptide might represent one form of agglutinin.     

外源海藻糖对啤酒酵母在热胁迫下的保护作用

为探究外源海藻糖对啤酒酵母在热胁迫下的保护作用,作者在3个热胁迫条件下检测外源海藻糖对啤酒酵母活力及活性的影响,并通过分析转录组数据对热胁迫下外源海藻糖对啤酒酵母的保护作用机理进行初步分析。结果表明,外源海藻糖可以提升啤酒酵母的耐热性,但具有一定限度,温度的升高和胁迫时间的延长导致不同浓度海藻糖的作用差别减小。另外,添加海藻糖可以增加酵母胞内海藻糖质量分数,添加海藻糖对啤酒酵母转录水平上的影响主要体现在核糖体的合成和相关功能上。结合本研究推测,外源海藻糖对啤酒酵母在热胁迫下的保护作用是通过增加胞内海藻糖质量分数实现的,上升的胞内海藻糖质量分数促进了核糖体合成及相关代谢,使核糖体功能增强,进而实现对啤酒酵母耐热性的增强。     

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

Utilization of distillery stillage from bioethanol production for lactic acid and feed production was studied. The lactic acid fermentation of the stillage was performed by Lactobacillus rhamnosus ATCC 7469 and maximal lactic acid concentration of 50.18 g L^− 1, yield of 0.90 g g^− 1, productivity of 1.48 g L^− 1 h^− 1 and viable cell number of 5 × 10⁹ CFU mL^− 1 were achieved. Solid residues with biomass remains after lactic acid fermentation were assessed for animal consumption. The content of proteins and ash decreased in the residues after the fermentation, whilst the content of oil and nitrogen free extract was higher when compared to unfermented samples. The digestible (17480.64 kJ kg^− 1) and metabolisable (17389.08 kJ kg^− 1) energies as well as digestibility (966.95 g kg^− 1) of the fermentation residue were very high. The in vitro assessment of L. rhamnosus ATCC 7469 survival in simulated gastric conditions has shown high survival rate (87%). In addition, this bacterium has shown good antimicrobial activity against the most important pathogens and capability to produce exopolysaccharide on different sugars present in animal diet. After effective lactic acid fermentation, the residues could be recommended as a high quality feed for monogastric animals.     

Characterization of the Saccharomyces bayanus‐type AGT1 transporter of lager yeast

Transport of maltose and maltotriose into the yeast cell is thought to be rate‐limiting in the utilization of these sugars. The maltose and maltotriose transporters Malx1, Agt1, Mtt1 and Mphx are present in different combinations in brewer's yeast strains, conferring different maltose and maltotriose transport characteristics on the strains. A new putative maltose/maltotriose transporter ORF was identified during whole genome sequencing of the lager strain WS34/70 (Y. Nakao et al., DNA Res., 2009, 16, 115–129). Sequence comparisons suggested that this putative α‐glucoside transporter might be a Saccharomyces bayanus counterpart of the Agt1 (Saccharomyces cerevisiae type) transporter. In the present work, the transporter coded by a SbAGT1 gene from a lager strain, A15 (and with the same sequence as the corresponding gene in WS34/70) was characterized. It is shown that this SbAGT1 encodes a functional α‐glucoside transporter with a wide‐substrate range, including maltose and maltotriose. Trehalose, α‐methylglucoside and sucrose were inhibitors, suggesting they are also substrates. The SbAgt1 transporter had similar affinities for maltose and maltotriose (17 ± 7 and 22 ± 2 m m , respectively) and a higher V_max for maltose than maltotriose (21 ± 7 and 12 ± 2 µmol min^?1 g dry yeast^?1, respectively). Copyright © 2012 The Institute of Brewing & Distilling     

Isolation of a lager yeast with an increased copy number of the YCK1 gene and high fermentation performance

The selection of yeast with good fermentation characteristics is critical for producing beer with desirable qualities. A yeast population was selected with an enhanced fermentation rate, referred to as high‐fermentation yeast (HFY), which was derived from the wild‐type Sacchromyces pastorianus yeast population (WTY). To identify genes that contribute to the fermentation performance, we compared the genetic profiles of the WTY and HFY populations by next‐generation sequencing. Several chromosomal regions were found to exhibit markedly different sequence coverage, suggesting chromosomal duplications and deletions, which might have occurred during selection of the HFY population. Among the genes with altered coverage, the copy number of the Saccharomyces eubayanus‐type YCK1 (SeYCK1) gene was almost two times higher in the HFY population than in the WTY population. The gene which is involved in glucose sensing in Saccharomyces cerevisiae was at a higher level in the HFY population throughout fermentation. These findings suggest that the chromosomal duplication of a region including the SeYCK1 gene locus of the HFY population is at least partially responsible for the differences in the fermentation properties between the WTY and HFY populations. © 2018 The Institute of Brewing & Distilling     

Evaluation of fermentation and aerobic stability of wet brewers' grains ensiled alone or in combination with various feeds as a total mixed ration

Wet brewer's grains (BG; 200 g kg^?1 dry matter(DM)) were ensiled alone or in combination with various dry feeds as a total mixed ration (TMR; 540 g kg^?1 DM) in laboratory silos. Ensilage was stopped at 40 days (experiment 1) or at 5, 20, 40 and 60 days (experiment 2) after storage. The composition of soluble sugars and the profiles of fermentation products were determined. The 60 day silages were subjected to aerobic deterioration and changes in silage temperature were recorded for 7 days. A rapid pH fall coupled with accelerated lactic acid production was observed in BG silage; soluble sugars, mainly composed of maltose and raffinose, completely disappeared within 5 days of ensiling. Prolonged storage, however, decreased lactic acid concentration and increased acetic acid greatly. Appreciable amounts of propionic acid and 1‐propanol were also produced in BG silage in the late stages of fermentation. When TMR silage was made, the decline in pH and the increase in lactic acid were delayed due to the low moisture content. Acetic acid production was enhanced from the beginning of storage, and mannitol accumulated in TMR silage. Yeast numbers were lower in TMR than in BG silage, but the changes were limited in the late stages of fermentation. When exposed to air, the temperature of BG silage increased after 3 days, whereas that of TMR silage appeared stable during the 7 days test. The results indicate that BG is a suitable by‐product for ensiling and, when ensiled with various feeds as a TMR, improved stability against aerobic deterioration can be expected. Copyright © 2003 Society of Chemical Industry     

Effects of Brewer's Spent Grain on the Quality and Dietary Fibre Content of Cookies

Dried and ground brewer's spent grain (BSG) was blended with soft wheat flour at levels of 5–25%. BSG preparations of fine (<212 μm), medium (212–425 μm) and coarse (425–850 μM) particle sizes were used in the production of wire‐cut cookies. The protein content decreased and the dietary fibre content (acid detergent fibre, neutral detergent fibre and total dietary fibre) increased, as the particle size of the BSG samples increased. The results indicated that BSG preparations with high dietary fibre content have potential as a source of dietary fibre. The effects of BSG on the quality and dietary fibre content of cookies have been investigated. Total dietary fibre (TDF) contents of the cookies supplemented with different particle size BSG increased significantly (p<0.05) as the addition level increased. Cookies prepared with BSG of medium and coarse particle sizes resulted in better properties in terms of Spread Ratio, Hunter color values and overall sensory score as compared to those made with BSG of fine particle size. Cookies made with medium and coarse particle size BSG gave better cookie properties up to the 15% addition and deteriorated significantly above this level (p<0.05).