Higher Lactic Acid Content Research Articles

Comparison between response surface methodology and genetic algorithm analysis to optimize lactic acid production by Lactobacillus rhamnosus and Lactobacillus acidophilus under ultrasonic pretreatment.

This work compared response surface methodology (RSM) and genetic algorithm (GA) analysis to optimize the lactic acid content by Lactobacillus rhamnosus PTCC 1637 and Lactobacillus acidophilus PTCC 1643 in a medium based on date syrup. Three parameters including concentrations of sucrose [10 and 20% (w/w)] and yeast extract [1, 2 and 3% (w/w)] along with different amplitudes of ultrasound (30kHz, 25 and 50%) were investigated in terms of their impacts on both viable cell counts and lactic acid production. Regarding RSM and GA, optimized samples were selected by achieving high lactic acid concentration. The results indicated that an increase in the amounts of sucrose and yeast extract led to increasing the cell growth and lactic acid production. Application of ultrasound at 25% amplitude significantly (P<0.05) stimulated the fermentation process. However, increasing the amplitude to 50% significantly (P<0.05) decreased the lactic acid production compared with the control samples. The best treatment was observed at 20% sucrose, 3% yeast extract and 25% ultrasound amplitude. The present results indicate that the best productivity of lactic acid can be achieved at appropriate fermentation conditions, including a suitable amplitude of ultrasound and supplementation of date syrup.

An investigation on fermentative profile, microbial numbers, bacterial community diversity and their predicted metabolic characteristics of Sudangrass (Sorghum sudanense Stapf.) silages.

ObjectiveThis study aimed to investigate the fermentation profiles, bacterial community and predicted metabolic characteristics of Sudangrass (Sorghum sudanense Stapf.) during ensiling.MethodsFirst-cutting Sudangrass was harvested at the vegetative stage and ensiled in laboratory-scale silos (1 L capacity). Triplicate silos were sampled after 1, 3, 7, 15, 30, and 60 days of ensiling, respectively. The bacterial communities on day 3 and 60 were assessed through high-throughput sequencing technology, and 16S rRNA-gene predicted functional profiles were analyzed according to the Kyoto encyclopedia of genes and genomes using Tax4Fun.ResultsThe Sudangrass silages showed good fermentation quality, indicated by higher lactic acid contents, and lower pH, butyric acid and ammonia nitrogen contents. The dominant genus Lactococcus on day 3 was replaced by Lactobacillus on day 60. The metabolism of amino acid, energy, cofactors and vitamins was restricted, and metabolism of nucleotide and carbohydrate was promoted after ensiling. The 1-phosphofructokinase and pyruvate kinase of bacterial community seemed to play important roles in stimulating the lactic acid fermentation, and the promotion of arginine deiminase could help lactic acid bacteria to tolerate the acidic environment.ConclusionHigh-throughput sequencing technology combined with 16S rRNA gene-predicted functional analyses revealed the differences during the early and late stages of Sudangrass ensiling not only for distinct bacterial community but also for specific functional metabolites. The results could provide a comprehensive insight into bacterial community and metabolic characteristics to further improve the silage quality.

Effect of molasses on fermentation quality of wheat straw ensiled with perennial ryegrass

Context Insufficient supply of silage has limited the development of animal husbandry in Tibet, where natural pasture may not meet requirements. Although wheat (Triticum aestivum L.) straw could be a supplementary forage, it is difficult to ensile. Mixing perennial ryegrass (Lolium perenne L.) and adding molasses may help to facilitate successful ensilage. Aims The objectives were to determine the proper mixing ratios of wheat straw and perennial ryegrass for silage, and to evaluate the effects of different levels of molasses on fermentation quality. Methods In Experiment 1, wheat straw was ensiled without perennial ryegrass or mixed at ratios of 4:1, 3:2 and 2:3 (fresh-weight basis). Fermentation quality was evaluated when the laboratory silos were opened after 7, 14, 30 and 60 days. In Experiment 2, a mixture of wheat straw and perennial ryegrass (2:3) was treated with 0%, 3%, 4% and 5% molasses (fresh-weight basis) and ensiled. Fermentation quality was determined at 7, 14, 30 and 60 days. Key results In Experiment 1, inclusion of perennial ryegrass significantly (P &lt; 0.05) increased lactic acid and water-soluble carbohydrate contents and the lactic acid:acetic acid ratio, and significantly (P &lt; 0.05) decreased pH and contents of ammonia-nitrogen, acetic acid, butyric acid and total volatile fatty acids. The 2:3 mixture of wheat straw ensiled with perennial ryegrass was judged the best, with the highest lactic acid content and lowest pH and butyric acid content (P &lt; 0.05). In Experiment 2, molasses addition significantly (P &lt; 0.05) increased lactic acid, water-soluble carbohydrate and dry matter contents, and significantly (P &lt; 0.05) decreased pH and ammonia-nitrogen content compared with the control. Trace amounts of propionic and butyric acids were observed in all silages. Fermentation quality was similar among all treatments with added molasses. Conclusions Considering the costs of additives, 3% molasses was most suitable for practical application when ensiling wheat straw with perennial ryegrass at an optimum ratio of 2:3. Implications This work may help to inform producers on efficient utilisation of wheat straw for silage making by demonstrating successful ensiling with perennial ryegrass and added molasses.

Biological additives improved qualities,

Context The amelioration of low-quality cheap feed for livestock production has become a huge challenge faced by the livestock producers coupled with the illicit disposal of the straw, which causes global environmental nuisance through burning and health impairment. Aims The purpose of this study is to examine the efficacy of biological additives on nutrient profiles, silage quality, in vitro rumen fermentation in different varieties of rice straw silage; ML4, ML10, ML21, ML24, MR219 and Putra-1 were ensiled with water (control), enzyme (E) and a combination of bacteria and enzyme (BE) in a complete randomised design (CRD) experiment. Methodology The rice straw varieties, obtained from the paddy research farm were chopped to ∼2–3 cm, treated according to the above treatments to attain 70% moisture content and compressed in a 1 L jar and ensiled for 30 days. Key results Crude protein (CP) in the treated rice straw silage was higher than in the control. The treatment with BE had a lower neutral detergent fibre (42.31%) and a lower acid detergent fibre (21.08%) concentration for Putra-1 than did other treatments (E and control) and varieties. For the silage extract, the lowest pH, NH3, butyric acid and propionic acid were obtained in the BE treatment in most of the rice straw varieties. In addition, straw treated with BE had the highest lactic acid content, in vitro gas production kinetics, digestibility, and rumen fermentation, compared with the E and control treatments. Conclusion This study showed that a BE treatment effectively improved the quality of rice straw silage, with the Putra-1 variety giving the most outstanding result. Implication Selection of the appropriate biological treatment and variety of rice straw is important to improve straw quality. However, the treated rice straw needs further evaluation for its in vivo efficacy.

Relationship between the Lactic Acid Content and Sour Taste of Broiler Broth and the Broth of Choshu-Kurokashiwa-a Japanese Jidori Chicken.

The present study aimed to determine whether lactic acid content is associated with the intensity of the sour taste of Choshu-Kurokashiwa broth. Chicken broth was prepared using breast (pectoralis major) and leg (thigh + drumstick) meat of male and female Choshu-Kurokashiwa and broilers. These broths were assessed by a screened and trained panel and analyzed for sour taste substances (lactic, citric, pyruvic, malic, succinic, acetic, phosphoric, aspartic, and glutamic acids) and pH. The sensory sour taste was significantly higher in the Choshu-Kurokashiwa breast broth than in the broiler breast broth (P>0.001), and no significant difference was observed in the leg broths among the breeds (P<0.05). Choshu-Kurokashiwa breast broth had a significantly higher lactic acid content than broiler breast broth (P<0.001). The leg meat broth of male Choshu-Kurokashiwa had a significantly lower lactic acid content than that of female Choshu-Kurokashiwa and broiler leg meat (P<0.01). The sensory sour taste score was significantly and positively correlated with lactic acid content in the breast broth (P<0.001), but not in the leg broth (P<0.1). No other organic acids were detected. Phosphoric acid and glutamic acid contents were higher in broiler broth than in Choshu-Kurokashiwa broth for both breast and leg meat (P<0.001). In the breast broth, the aspartic acid content was not significantly different (P>0.1), and in the leg broth, it was higher in broiler and female Choshu-Kurokashiwa broth than in male Choshu-Kurokashiwa broth (P<0.001). The present study suggests that high lactic acid content contributes to the sour taste of the Choshu-Kurokashiwa breast broth and demonstrated that the lactic acid content is an essential indicator for determining the sour taste of Choshu-Kurokashiwa breast meat.

HIGH LACTIC ACID PRODUCTION BY Lactobacillus sp. V156 ISOLATED FROM VIETNAMESE FERMENTED MUSTARD GREEN

In the present study, a lactic acid producing bacterium was isolated and screened from fermented mustard green. The selected bacterial strain (V156) was classified into genus Lactobacillus. High lactic acid concentration of 101.6 g/L and productivity of 2.82 g/L/h were efficiently achieved by Lactobacillus sp. V156 after 36 h of cultivation in fed-batch fermentation using ammonium hydroxide as the neutralizing agent. The production of high lactic acid in short cultivation time demonstrates that Lactobacillus sp. V156 is a promising strain for L-lactic acid production

Effects of hexanoic acid on microbial communities, fermentation, and hygienic quality of corn silages infested with toxigenic fungi.

This study aims to reveal the effects of hexanoic acid on the microbial communities, fermentation, and the hygienic quality of corn silages with or without fungal infection. Fungal-infested (FI) and non-infested (NFI) whole-crop corn samples were separately ensiled without (control, CON) or with hexanoic acid (Hex, 90% purity) at 0.2g·kg-1 fresh weight (FW). The addition of Hex accelerated the pH decline during the first 5 days of ensiling regardless of fungal infestation. The lactic acid (LA) concentration in Hex silages was lower than that in CON during 45 days of ensiling; however the FI-Hex silage had the highest LA concentration among treatments on day 90. The Hex silage showed lower aflatoxin B1 (AFB1 ), zearalenone (ZEA), and deoxynivalenol (DON) concentrations than CON for FI silages. On day 5, the addition of Hex decreased the relative abundance of Klebsiella, Pantoea, and Enterobacter compared with CON, regardless of fungal infestation. This inhibitory effect lasted until day 90 for NFI silages but disappeared for FI silages on day 90. The fungal infestation resulted in the accumulation of Candida (34.05%) and Wickerhamomyces (19.46%). Hex decreased the relative abundance of Asperigillus, Issatchenkia, and Penicillium for NFI silages on day 5; however, its inhibitory effects were not observed in FI silages on day 5. Fungal infestation was associated with poor fermentation and hygienic quality of corn silage. Adding Hex accelerated the pH decline and maintained the antifungal activity until 90 days of ensiling, attenuating adverse effects of fungal infestation on the fermentation and preventing the accumulation of mycotoxins in corn silages. © 2021 Society of Chemical Industry.

Enhanced fermentative lactic acid production from source-sorted organic household waste: Focusing on low-pH microbial adaptation and bio-augmentation strategy

Lactic acid (LA) production at low pH could significantly reduce the need for neutralizing agents, leading to reduction of operational costs. In the present study, LA production at acidic conditions was investigated using source-sorted organic household waste (SSOHW). Controlling the pH at low value (i.e. 5.0) and bio-augmenting with Pediococcus acidilactici led to a concentration of 39.3 ± 0.5 g-LA/L with a yield of 0.75 ± 0.02 g-LA/g-sugar. In contrast, secondary fermentation at higher pH level (i.e. 5.5 and 6.0) resulted in complete LA degradation. Subsequently, consecutive batch fermentations were conducted to adapt P. acidilactici to SSOHW and improve the LA production. Results showed that P. acidilactici could successively adapt in the SSOHW reaching a relative abundance above 2.8% at adaptation process. The added P. acidilactici ensured a high concentration of LA at three consecutive generations, achieving an increment above 18% compared to control test (abiotic augmentation). Moreover, adaptation processes (i.e. maintaining pH at 4.0 or stepwise decreasing the pH from 5.0 to 4.0) significantly improved LA concentration and productivity at the pH of 4.0. Overall, the results provide a promising method to reduce the LA production costs using residual resources.

The effect of biological additive on the fermentation quality of whole-crop rye silage

The effect of biological additive on the fermentation quality of whole-crop rye silage

Purification of organic acids using electrodialysis with bipolar membranes (EDBM) combined with monovalent anion selective membranes

• EDBM used to purify a mixture of lactate and citrate as a simulated beet molasses solution. • The use of a monovalent selective anion exchange membrane gives higher purity than with a standard AEM. • Adjustment of the feed to pH > 9.0 improves separation due to the larger size of the citrate anion. • A volume ratio of 10:1 acid:feed gives 153 g/L lactic acid of 95% purity with <2.7 KWh per kg lactate. • The BP-A-C configuration is more energy efficient than BP-A. The feasibility of using electrodialysis with bipolar membranes (EDBM), combined with monovalent selective anion exchange membranes was investigated to purify organic acids from fermentation broths or wastewater streams. A simulated beet molasses feed containing a mixture of monobasic lactic acid and polybasic citric acid was used for this purpose. The impact of the feed pH, the configuration of the membrane stack and the voltage applied on the selectivity of the process was investigated. At a pH of 9–10 and an electric field intensity of 9 V/cm, a lactic acid product with a purity of at least 97% can be obtained by using both two chamber (BP-A) and three chamber (BP-A-C) configurations with the monovalent selective membrane. When using the BP-A configuration, the hydroxide ions generated by the bipolar membrane compete with the lactate anions to move into the acid solution and so the energy efficiency is lower than with the BP-A-C configuration. To mimic a multiple pass process and increase the lactic acid concentration of the final product, experiments were performed across a range of volume ratios between the feed and acid solutions. As this ratio is varied, the purity of lactic acid produced remains higher than 95% while the energy consumption is essentially unaffected. Due to the osmotic flow of water during experiments, the highest lactic acid concentration that can be achieved is limited to 153 g/L at a volume ratio (V A : V F ) of 1:10.

The Role of Lactic Acid on Wound Healing, Cell Growth, Cell Cycle Kinetics, and Gene Expression of Cultured Junctional Epithelium Cells in the Pathophysiology of Periodontal Disease.

Lactic acid (LA) is short-chain fatty acid, such as butyric acid and propionic acid, that is produced as a metabolite of lactic acid bacteria, including periodontopathic bacteria. These short-chain fatty acids have positive effects on human health but can also have negative effects, such as the promotion of periodontal disease (PD), which is caused by periodontal pathogens present in the gingival sulcus. PD is characterized by apical migration of junctional epithelium, deepening of pockets, and alveolar bone loss. Thus, the junctional epithelial cells that form the bottom of the gingival sulcus are extremely important in investigating the pathophysiology of PD. The aim of this study was to investigate the effect of LA on wound healing, cell growth, cell cycle kinetics, and gene expression of cultured junctional epithelium cells. The results showed that stimulation with 10 mM LA slowed wound healing of the junctional epithelial cell layer and arrested the cell cycle in the G0/G1 (early cell cycle) phase, thereby inhibiting cell growth. However, cell destruction was not observed. LA also enhanced mRNA expression of integrin α5, interleukin (IL)-6, IL-8, intercellular adhesion molecule-1, and receptor activator of nuclear factor kappa-B ligand. The results of this study suggest that stimulation of junctional epithelial cells with high concentrations of LA could exacerbate PD, similarly to butyric acid and propionic acid.

The effect of rice types on chao properties during fermentation

Chao is a typical Indonesian dish from Pangkep Regency that is relatively unknown to the general public. Chao is made from fermented fish, which is subsequently fermented with rice. Chao has the properties of pasta-like, light-brown color, unique flavor, slightly acidic and salty taste. Pangkep communities typically use chao as a seasoning, condiment ingredient, or as a side dish. Due to the product's attractive features, which resemble stale food, make it less appealing to consumers. It necessitates innovation and processing technologies in order to improve the quality of Chao products. This research this study aimed to find out the effect of rice variations including white rice, red rice and black rice on the characteristics of Shrimp Chao during fermentation. The testing parameters in this study were total Lactic Acid Bacteria (LAB), total lactic acid, pH, and organoleptic. The highest LAB growth was found in the red rice that is 7.67 log cfu/g with the lowest pH value of 6.02 and the highest lactic acid content (1.8%). The best organoleptic test results own by white rice-based shrimp chao with preference average score of 3.85 and red rice 3.78 which imply “like” in organoleptic scale scoring.

Preliminary determination of antibacterial substances during anaerobic preservation of food waste and their effects on methanogenesis

Food waste can easily breed bacteria and produce odour during production, collection, transportation, preservation and disposal. This work studied the effects of aerobic preservation and anaerobic preservation on the antibacterial and antiseptic properties of food waste and subsequent methane production by anaerobic fermentation. Compared with aerobic preservation, the concentration of lactic acid produced on the 5th day of anaerobic preservation increased by 2.01 times, the pH decreased rapidly and the number of Escherichia coli was reduced by 99.96% on the 7th day; all these changes could effectively inhibit the activity of spoilage bacteria. The results of the biological toxicity test showed that lactic acid and acetic acid were the main antibacterial substances in anaerobic preservation. The biological toxicity of lactate or acetate was significantly lower than that of the corresponding organic acid molecules. When food waste enters the anaerobic digestion reactor after preservation, materials with high lactic acid concentration are greatly diluted, which will not affect the methane fermentation process, but can lead to elevate biogas production. These observations are consistent with the conclusion obtained by kinetic analysis that anaerobic preservation has a faster hydrolysis rate and a shorter system stagnation period than aerobic preservation. Therefore, anaerobic preservation is a suitable way of storing food waste, and it can promote methane fermentation.

L-Lactic Acid Production Using Engineered Saccharomyces cerevisiae with Improved Organic Acid Tolerance.

Lactic acid is mainly used to produce bio-based, bio-degradable polylactic acid. For industrial production of lactic acid, engineered Saccharomyces cerevisiae can be used. To avoid cellular toxicity caused by lactic acid accumulation, pH-neutralizing agents are used, leading to increased production costs. In this study, lactic acid-producing S. cerevisiae BK01 was developed with improved lactic acid tolerance through adaptive laboratory evolution (ALE) on 8% lactic acid. The genetic basis of BK01 could not be determined, suggesting complex mechanisms associated with lactic acid tolerance. However, BK01 had distinctive metabolomic traits clearly separated from the parental strain, and lactic acid production was improved by 17% (from 102 g/L to 119 g/L). To the best of our knowledge, this is the highest lactic acid titer produced by engineered S. cerevisiae without the use of pH neutralizers. Moreover, cellulosic lactic acid production by BK01 was demonstrated using acetate-rich buckwheat husk hydrolysates. Particularly, BK01 revealed improved tolerance against acetic acid of the hydrolysates, a major fermentation inhibitor of lignocellulosic biomass. In short, ALE with a high concentration of lactic acid improved lactic acid production as well as acetic acid tolerance of BK01, suggesting a potential for economically viable cellulosic lactic acid production.

Silage fermentation characteristics and microbial diversity of alfalfa (Medicago sativa L.) in response to exogenous microbiota from temperate grasses.

The objective of this study was to explore the microbiological factors that cause the difference in silage fermentation characteristics between grass and legume. Specifically, the effects of epiphytic microbiota from alfalfa, oat and Italian ryegrass on ensiling characteristics and microbial community of alfalfa were assessed. By γ-ray irradiation sterilization and microbiota transplantation technology, the sterile alfalfa was inoculated as follows: (i) aseptic water (STAL); (ii) epiphytic bacteria from alfalfa (ALAL); (iii) epiphytic bacteria from oat (ALOT); (iv) epiphytic bacteria from Italian ryegrass (ALIR). Alfalfa at the initial flowering stage was ensiled in laboratory-scale silos for 1, 3, 7, 14, 30 and 60 days. Compared with ALAL and ALIR, higher lactic acid contents and ratio of lactic acid to acetic acid, and lower acetic acid, propionic acid, ethanol and ammonia nitrogen contents were observed in ALOT after 60 days of fermentation. In each treated group, Lactobacillus was the most dominant genus after 60 days of ensiling. Relatively higher abundance of Weissella, Hafnia-Obesumbacterium, Enterobacteriaceae or hetero-fermentative Lactobacillus was found in ALAL and ALIR after 60 days. Co-occurrence network analysis proved Pediococcus and Lactococcus were pivotal in deciding the fermentation pattern of alfalfa silage. According to the 16S rRNA gene-predicted functional profiles, the metabolism of amino acids was inhibited by the epiphytic microbiota from oat. Overall, ALOT showed a homo-fermentative process, whereas ALAL and ALIR exhibited a hetero-fermentative pattern. Furthermore, the exogenous microorganisms inhibiting the metabolism of amino acids can be a good potential source to improve the silage quality of legume forage.

Effect of epiphytic microbiota from napiergrass andSudan grass on fermentation characteristics and bacterial community in oat silage.

To investigate the effects of epiphytic microbiota from napiergrass and Sudan grass on ensiling characteristics and microbial community of oat silage. By γ-ray irradiation sterilization and microbiota transplantation technology, the sterilized oat was inoculated as follows: (a) aseptic water (STOT), (b) epiphytic bacteria on oat (OTOT), (c) epiphytic bacteria on napiergrass (OTNP) and (d) epiphytic bacteria on Sudan grass (OTSD). STOT remained in the unfermented state based on similar chemical components with fresh oat. Compared with OTOT and OTSD, higher lactic acid content and ratio of lactic acid to acetic acid, and lower pH, acetic acid and ammonia nitrogen contents were observed in OTNP after 60days of ensiling. At the late stage, Lactobacillus was the most predominant in each group. Lactococcus was eventually replaced by Lactobacillus in OTSD, whereas Lactococcus was found throughout the whole ensiling process in OTNP. Higher abundance of Weissella was observed in OTSD at the early and late stages. The result of co-occurrence network analysis proved that Lactococcus was pivotal in determining the silage fermentation pattern during ensiling. According to the 16S rRNA gene-predicted functional profiles, the inoculation of epiphytic microbiota from oat enhanced the metabolism of amino acids, whereas the inoculation of epiphytic microbiota from napiergrass and Sudan grass accelerated the carbohydrate metabolism. The epiphytic microbiota on napiergrass promoted a homo-fermentative process, whereas the epiphytic microbiota on oat and Sudan grass facilitated a hetero-fermentative pattern in oat silage, which was closely related to the abundance and metabolism of Lactococcus, Weissella and Lactobacillus. The exogenous microorganisms that promote the carbohydrate metabolism and inhibit the metabolism of amino acids could be a good potential source to improve the silage quality of temperate grass.

Effects of malic or citric acid on the fermentation quality, proteolysis and lipolysis of alfalfa silage ensiled at two dry matter contents.

This study evaluated the effects of two organic acids on the fermentation of alfalfa silages at different dry matter (DM) contents. Alfalfa was wilted to DM contents of 30% (moderately low) and 38% (normal) and ensiled without additives (control) or treated with 0.6% fresh matter DL-malic acid (MA) or 0.6% fresh matter citric acid (CA) for 60days. After ensiling, silages with a normal DM were higher in pH, water-soluble carbohydrates (WSC) and DM loss (p<0.05) when compared to silages ensiled at a moderately low DM. The higher DM content also limited proteolysis in silages indicated by lower concentrations of ammonia N (NH3 -N). Compared with the control group, MA and CA-treated silages had lower pH, lower concentrations of acetic acid and NH3 -N but higher concentrations of lactic acid. The addition of MA and CA reduced DM losses in silages when compared to the control group except for MA-treated silage at a moderately low DM in which only numerically lower DM loss was observed. Malic acid and CA also resulted in a higher proportion of polyunsaturated fatty acids, especially in silages with a moderately low DM. Including MA and CA could promote silage fermentation, limit proteolysis and lipolysis at the lower and medium-to-high end of DM contents in alfalfa silages.

Separating the effects of chemical and microbial factors on fermentation quality and bacterial community of Napier grass silage by using gamma-ray irradiation and epiphytic microbiota transplantation

This study aimed to separate the effects of chemical composition and epiphytic microflora on the fermentation quality and bacterial community of Napier grass silage. Napier grass was harvested in two vegetative stages (Early, EG; Late, LG) with 24 or 28% dry matter, cut into theoretical lengths of 2–3 cm, and ensiled in bag-type silos containing 450 g fresh matter for 30 d. A 2 × 2 factorial arrangement of treatments (2 chemical composition × 2 epiphytic microbiota) in a completely randomized design were as follows: EG epiphytic microbiota + gamma-ray irradiated EG (EMEG), LG epiphytic microbiota + gamma-ray irradiated EG (LMEG), EG epiphytic microbiota + gamma-ray irradiated LG (EMLG), and LG epiphytic microbiota + gamma-ray irradiated LG (LMLG). Triplicates per treatment were sampled after 30 d of ensiling for fermentation quality and bacterial community analyses. The maturity of Napier grass had a great impact on its chemical composition and epiphytic microflora at harvest. Silages made from irradiated EG (EMEG and LMEG) had higher lactic acid concentration and lactic:acetic acid ratio, and lower pH value and ammonia nitrogen (NH3-N) concentration than the silages made from irradiated LG (EMLG and LMLG). Species differential analyses showed that the chemical composition variation significantly affected the relative abundance of Lactobacillus, Lactococcus, Enterobacter, Serratia, unclassified Lactobacillales, Leuconostoc and Pediococcus in EMEG and EMLG silages. While there was no effect of epiphytic microbial variation on the relative abundance of bacterial genera in EMLG and LMLG silages. These results manifested that, in this study, chemical composition rather than epiphytic microflora affected the succession of bacterial community in Napier grass silages, thereby affecting the final fermentation quality.

American pale Ale craft beer: Influence of brewer's yeast strains on the chemical composition and antioxidant capacity

This study aimed to evaluate the influence of using four different Saccharomyces cerevisiae strains on the phenolic compounds, antioxidant capacity (AOX), organic acid, sugar, and alcohol profiles of American Pale Ale (APA) craft beer. US-05 yeast presented a lower fermentation capacity but originated a beer with suitable ethanol content, higher lactic acid content, and lower acetic acid and succinic acid contents. Furthermore, it presented higher quantities of catechins and procyanidin B1, which resulted in a higher AOX. M15 yeast originated a beer with lower ethanol content and AOX and higher malic and formic acid contents. Beers made with BRY-97 yeast had higher ethanol content, while those made with S-04 yeast presented higher glycerol content. Several factors can affect beer quality. This study demonstrated that the type of yeast strain used in the APA craft beer brewing has a significant impact not only on the fermentative process but also on the functional characteristics of the products.

Antimicrobial properties of traditional kefir: An in vitro screening for antagonistic effect on Salmonella Typhimurium and Salmonella Arizonae

The rise of antibiotic resistance in Salmonella has necessitated the need for alternative ways of preventing and controlling infections. Fermented products have been recognised to have prophylactic and therapeutic properties against diseases. This study focused on the analysis of antagonistic effect of two different traditional kefir grains on Salmonella Arizonae and Salmonella Typhimurium after 24 and 48 h fermentation. Kefir supernatants were analysed for ethanol, organic acid and protein composition using gas chromatography, high performance liquid chromatography and shotgun proteomics, respectively. Salmonellae were rapidly eradicated in kefir possibly due to action of lactic acid as kefir cell-free supernatant contained high concentrations of lactic acid ranging from 83.59 to 229.92 mm. Other molecules with recognised antibacterial activities including carbonyl compounds, histone and cathelicidin were detected in the soluble phase that could have provided synergistic effect with the organic acids.