Undesirable Microbes Research Articles

Novel flaxseed mucilage-based probiotic film: Application to sheep Sicilian cheese preservation

Edible probiotic films incorporated by probiotics can be used to keep away from undesirable microbes on the surface of the cheese to improve its quality and promote beneficial effects on consumer health. In this study, flaxseed, Lactobacillus rhamnosus and Lactobacillus acidophilus as probiotics were used to produce active edible packaging and evaluate its application in the sheep Sicilian cheese surfaces stored 10 days at 4°C. Microbiological, physicochemical, sensorial quality, antibacterial and antioxidant effects of cheeses were studied. The flaxseed mucilage-probiotic film improved cheese preservation by reducing the weight loss, preserving the pH and colour. Advantageously, flaxseed coating allowed improving probiotic viability throughout storage period. Native microbiota counts remained under safe levels. Probiotic coating cheeses exhibited 12.8±0.25 mm of maximum diameter inhibition against Listeria monocytogenes and enhanced oxidation (maximum DPPH inhibition: 51±0.33%) with acceptable sensorial properties for consumers. Hence, flaxseed mucilage probiotic film has proved to be suitable for quality preservation of functional foods.

Factors affecting nutrient losses in hay production

AbstractThe primary objective of haymaking is to dry forage adequately to inhibit the growth of undesirable microbes and halt residual plant enzymatic activity that causes nutrient losses. During the field and storage phases of haymaking, the environment, management practices, and other factors influence the extent of dry matter losses. This review discusses these factors and the strategies that have been developed to mitigate nutrient losses. A major emphasis was placed on hay microbiome dynamics, as it has been scarcely studied despite its importance on nutrient losses during storage and harvest, especially under humid conditions. The effects of cutting height, mower type, and swath manipulation on soil contamination were discussed. Also, the impact of environmental conditions and swath manipulation on wilting time was analysed for humid and arid conditions. Special attention was given to design improvements in harvesting equipment to reduce wilting time and field losses. Furthermore, we assessed the nutrient losses during storage caused by microbial and residual plant enzymatic activity resulting from excessive moisture at baling or re‐introduced moisture during storage. The spoilage extent during storage depends on bale moisture, size, density, shape, wrapping, forage type, and storage facilities. A Venn diagram analysis showed that each phase of haymaking process has a unique microbiome and that certain fungal and bacterial genera could be shared across more than one hay production phase. To take corrective actions, hay producers need to be aware of the increased susceptibility to nutrient losses associated with particular field and storage practices, environmental conditions, and forage types.

Controlling microbial population in livestock and poultry industry using electrolyzed water as an emerging technology for ensuring food safety

Poultry and livestock contribute a significant amount of energy and protein to the human diet. However, a main concern is the undesirable microbial population from the poultry and livestock system that may cause diseases in both humans and animals. Electrolyzed water has shown broad-spectrum sanitization efficiency and gained considerable popularity. This review aims to provide an overview of the use of electrolyzed water under different environment conditions for sanitization in livestock and poultry systems. Electrolyzed water serves as an excellent antimicrobial and anti-biofilm agent against various pathogenic, disease-producing, and undesirable microbes in every step of the livestock and poultry sectors from farm to fork. The synergistic effects of the oxidation reduction potential, pH, and chlorine concentration of electrolyzed water enable its potential and prompt mechanism for controlling and eliminating various microorganisms. Compared to other conventional disinfectants, electrolyzed water has been shown to be more efficient and effective. As an environmentally-friendly sanitizer, electrolyzed water has been applied in livestock and poultry production and processing sectors such as animal drinking water, feed decontamination, house sanitation, transportation system, slaughterhouse sanitation, meat-processing industry decontamination, sanitization of milk-processing industries, hatchery and eggshell decontamination. This review is aimed to discuss the microbial control in livestock and poultry industry by applying electrolyzed water as a novel sanitizer.

The impact of environmental conditions and milk type on microbial communities of wooden vats and cheeses produced therein

Wooden vats are used in the production of some traditional cheeses as the biofilms on wooden vat surfaces are known to transfer large quantities of microbes to cheese. Variability in microbial communities on wooden vats could lead to inconsistent cheese production. In the present study, the influences of environmental conditions and milk type (raw or heat-treated) on the microbial composition of vat biofilms and cheeses made in the vats were studied using amplicon sequencing of bacterial 16S rRNA and fungal internal transcribed spacer genes. Results showed that the microbial composition of biofilms was influenced by environmental conditions but not the milk type used in cheese production. The microbial composition of cheeses can be further affected by bacterial contributions from milk and the selective forces of environmental conditions. Results of this study suggest that controlling environmental conditions could maintain a more consistent microbial composition of biofilms on wooden vats and resulting cheeses. The use of wooden vats coupled with heat-treated milk at one or more stages of cheese production might be a viable approach to produce cheese with high microbial diversities and reduce risks of undesirable microbes related to food safety and quality.

Effects of cellulase and xylanase on fermentative profile, bacterial diversity, and in vitro degradation of mixed silage of agro-residue and alfalfa

The objective was to determine effects of cellulase, xylanase, and commercial fibrolytic enzymes on fermentation quality, aerobic stability, bacterial community, and in vitro degradation of mixed silages. Mixtures of alfalfa, wheat bran, and rice straw [80:15:5 on a fresh matter (FM) basis] were ensiled for 1, 3, 5, 7, 15, 30, and 45 d after treatment with: distilled water (control, C); cellulase (E); xylanase (X); or commercial fibrolytic enzymes (EX), with all enzyme preparations applied at 100 U/g FM. The 45-day silages were subjected to an in vitro degradation test. Each of the three enzyme-treated groups enriched relative abundance (RA) of Lactobacillus, Weissella, and Stenotrophomonas maltophilia, increased water soluble carbohydrate (WSC) concentrations, and extended aerobic stability over 384 h, but concurrently inhibited growth of undesirable microbes (i.e., Acinetobacter sp, Lelliottia amnigena, and Sphingomonas sp), reducing pH and concentrations of ammonia nitrogen (AN), butyric acid (BA) and propionic acid (PA). Compared to C, adding X or EX increased the RA of L. paralimentarius and L. parabrevis, enhanced accumulation of acetic acid (AA) and crude protein (CP), and reduced hemicellulose content. Furthermore, E group silage had the highest abundance of W. cibaria. In addition, EX enriched RA of Bacillus velezensis, reduced AN concentration, increased DM degradability, total VFA production, and gas production during in vitro incubation. In conclusion, addition of X or EX enhanced ensiling by enhancing concentrations of AA; however, EX was the most promising enzyme, based on reducing AN concentration and increasing DM content and DM degradability.Graphical

Disease prevention and mitigation in US finfish aquaculture: A review of current approaches and new strategies

AbstractIn the United States, the aquaculture industry has not seen the same levels of growth in production as other countries—made evident by the $17 billion seafood trade deficit estimated in 2020. Nevertheless, aquaculture remains an important industry fully capable of supplementing the domestic seafood supply and reducing the US seafood trade deficit. Infectious diseases is one of several factors that threatens the capability and sustainability of the aquaculture industry, highlighting the importance of effective control strategies for these pathogens. Antimicrobial products are often used to control and eliminate undesirable microbes in effort to prevent or mitigate the impacts of infectious diseases. Some pathogens are capable of adapting to and resisting the antimicrobial effects, escalating the challenges associated with disease management in aquaculture. Antimicrobial resistance (AMR) is now recognised by numerous national and international agencies as a top global health concern and is problematic for US aquaculture. Currently, disease prevention and mitigation strategies utilised by US finfish aquaculture can be broken down into three levels; comprehensive protocols (biosecurity, disease response), good husbandry strategies (stress management, proper diet, optimal environment) and effective antimicrobial products (biocides, therapeutics). This review will discuss how each level contributes differently to the overall protection of fish from pathogens. In the era of AMR, this review will also highlight current and emerging alternative strategies that do not rely on traditional antimicrobial products (e.g., vaccines, dietary supplements, novel antimicrobial, stock selection) for disease prevention and mitigation.

Abiotic and biotic filters determine the response of soil bacterial communities to manure amendment

Manure amendments are a common soil amendment in forage and row cropping systems used to provide plant-available nutrients, build soil organic matter, and enhance soil health. Many of the benefits of manure applications are thought to be driven via their impacts on soil microbial communities. However, manure amendments may also introduce potential undesirable microbes (pathogens, or those with antibiotic resistance elements) to soils. Despite the widespread use of manure amendments and their importance in agricultural systems, the forces governing the assembly of bacterial communities in soil in response to manure amendments are poorly characterized, limiting our ability to predict their impacts on soil communities. We constructed soil microcosms using five soils from different locations to investigate the impacts of liquid dairy manure on bacterial communities. Moreover, we used combinations of autoclaved liquid dairy manure and soils to determine the roles of abiotic and biotic factors in the response of indigenous soil communities to manure and the fate of manure-borne bacteria. Bacterial amplicon sequence variants (ASVs) that responded to manure amendment were largely dependent on soil origin. Initial shifts in soil communities after manure amendment were driven by the introduction of manure-borne taxa. However, introduced taxa died off rapidly while some indigenous taxa increased in relative abundance over time. Introduced taxa died off even in the absence of indigenous microbiota, suggesting that the soil abiotic environment is a strong barrier to colonization by manure-borne bacteria. Finally, autoclaved manure amended to soil elicited a similar response from indigenous soil microbes as did live manure, indicating that organic matter, nutrients, or other physiochemical factors associated with manure amendments are responsible for changes in indigenous soil populations.

Innovative utilization of herbal residues: Exploring the diversity of mechanisms beneficial to regulate anaerobic fermentation of alfalfa

In order to increase the utilization of herbal residues, realize efficient utilization of resources, the bacterial community and anaerobic fermentation characteristics of alfalfa ensiling treated with 36 kinds of herbal residues were studied. All the herbal residues improved the anaerobic fermentation quality in different degrees, indicated by lower pH, NH3-N and butyric acid concentrations. However, the contents of lactic and acetic acids varied widely in silage with different herbal residues. Pearson’s correlation analysis showed that the improved fermentation quality was closely associated with the variation of lactic acid bacteria community. Consequently, the herbal residues could improve anaerobic fermentation quality by stimulating desirable Lactobacillus species and inhibiting undesirable microbes. This study provides new insights for efficient utilization of herbal residues.

Changes in chemical composition, structural and functional microbiome during alfalfa (Medicago sativa) ensilage with Lactobacillus plantarum PS-8.

Improving silage production by adding exogenous microorganisms not only maximizes nutrient preservation, but also extends product shelf life. Herein, changes in the quality and quantity of Lactobacillus plantarum PS-8 (PS-8) -inoculated alfalfa (Medicago sativa) during silage fermentation were monitored at d 0, 7, 14, and 28 (inoculum dose of PS-8 was 1 × 105 colony forming units [cfu]/g fresh weight; 50 kg per bag; 10 bags for each time point) by reconstructing metagenomic-assembled genomes (MAG) and Growth Rate InDex (GRiD). Our results showed that the exogenous starter bacterium, PS-8 inoculation, became the most dominating strain by d 7, and possibly played a highly active role throughout the fermentation process. The pH value of the silage decreased greatly, accompanied by the growth of acid-producing microorganisms namely PS-8, which inhibited the growth of harmful microorganisms like molds (4.18 vs. 1.42 log cfu/g) and coliforms (4.95 vs. 0.66 log most probable number [MPN]/g). The content of neutral detergent fiber (NDF) decreased significantly (41.6% vs. 37.6%; dry matter basis). In addition, the abundance and diversity of genes coding microbial carbohydrate-active enzymes (CAZymes) increased significantly and desirably throughout the fermentation, particularly the genes responsible for degrading starch, arabino-xylan, and cellulose. Overall, our results showed that PS-8 was replicating rapidly and consistently during early- and mid-fermentation phases, promoting the growth of beneficial lactic acid bacteria and inhibiting undesirable microbes, ultimately improving the quality of silage.

Production, characteristics and application of whey protein films activated with rosemary and sage extract in preserving soft cheese

Active packaging can be utilized to keep away from undesirable microbes on the surface of the cheese, prolong its shelf life, and improve its quality. The objective of this study was to use whey protein concentrate (WPC) and aqueous rosemary and sage extracts to produce active edible packaging materials. The antioxidant activity of the extracts was evaluated along with their total phenolic and flavonoid contents. LC/DAD/ESI-MSn analysis was used for the qualitative characterization of extracts and their main compounds were quantified using HPLC methods. Films were characterized according to their physicochemical and tensile properties. They were applied for coating soft cheese surfaces stored 60 days of cold storage at 4 °C. Both infusions showed almost similar antioxidant activity, although differences were detected in their total phenolic and flavonoid contents. Their phytochemical analysis revealed the presence of polyphenols. No significant differences in film thickness and moisture content were detected among the films. The presence of rosemary infusion did not significantly influence the mechanical properties of the films; while, sage infusion reinforced films compared to the control film. In the cheese samples coated with edible films fortified with infusions no spoilage or pathogenic bacteria appeared until the end of storage days.

Improving Quality of Sunn Hemp (Crotalaria Juncea L.) Foliage as Roughage Source for Ruminants by using Microorganisms

This study aims to investigate the chemical composition, fermentation characteristics, and in vitro ruminal digestibility efficiency of Sunn hemp silage with Fermented juice of epiphytic lactic acid bacteria (FJLAB) and bacillus subtilis. The experiment was designed in a CRD. Five dietary treatments were fresh Sunn hemp (FS, the positive control), Sunn hemp silage (SS, the negative control), Sunn hemp silage with B. subtilis (SSB), Sunn hemp silage with FJLAB (SSL), and SSB plus FJLAB (SSBL). The results showed the OM content of Sunn hemp silage was decreased (p < 0.05), but fiber contents (NDF, ADF, cellulose, and hemicellulose) were increased when compared with fresh Sunn hemp. However, SSL and SSBL could improve nutrition values (higher CP Reduction efficiency; p < 0.01, decrease cellulose; p < 0.01, and hemicellulose content; p < 0.10) and quality grading of Sunn hemp silage when compare with the negative control which did not affect to CP and EE values. Furthermore, FJLAB reduced fiber content and increase CP content of Sunn hemp silage, whereas B. subtilis presented the opposite results. However, the combination of FJLAB and B. subtilis showed the best treatment of Sunn hemp silage of this experiment (the highest CP and EE Reduction efficiency, ruminal gas production, and organic matter degradability; OMD).
 HIGHLIGHTS
 
 Pyrrolizidine Alkaloids, a toxin associated with disease in ruminants, found in Sunn hemp is completely destroyed by anaerobic microorganisms of silage
 The fermentation process of silage was improved by increasing lactic acid production and decreasing pH value to inhibit the growth of undesirable microbes
 Combination of fermented juice of epiphytic lactic acid bacteria (FJLAB) and Bacillus subtilis, lactic acid producer, for Sunn hemp silage treatment yielded the highest lactic acid production and nutritive values
 
 GRAPHICAL ABSTRACT

Improved performance and microbial community dynamics in anaerobic fermentation of triticale silages at different stages

Production of high-quality grass-based silages by microbial-mediated anaerobic fermentation is an effective strategy in livestock farms. In the present study, an ensiling process was used to preserve and enhance fermentative metabolites in triticale silages with novel inoculants of Lactobacillus rhamanosus -52 and, Lactobacillus rhamanosus-54. Triticale silages treated with LAB predominantly had lower pH values than control silages due to rapid changes of microbial counts. LAB addition improved anaerobic fermentation profiles showing higher lactic acid, but lower acetic acid and butyric acid concentrations. A background microbial dynamic study indicated that the addition of L. rhamanosus-52 and L. rhamanosus-54 improved silage fermentation, enriched Lactobacillus spp., and decreased microbial richness with diversity, leading to increased efficiency of lactic acid fermentation. In conclusion, LAB treatment can increase silage quality by enhancing the dominance of desirable Lactobacillus while inhibiting the growth of undesirable microbes.

Potential Replacements for Antibiotic Growth Promoters in Poultry: Interactions at the Gut Level and Their Impact on Host Immunity.

The chicken gastrointestinal tract (GIT) has a complex, biodiverse microbial community of ~ 9 million bacterial genes plus archaea and fungi that links the host diet to its health. This microbial population contributes to host physiology through metabolite signaling while also providing local and systemic nutrients to multiple organ systems. In a homeostatic state, the host-microbial interaction is symbiotic; however, physiological issues are associated with dysregulated microbiota. Manipulating the microbiota is a therapeutic option, and the concept of adding beneficial bacteria to the intestine has led to probiotic and prebiotic development. The gut microbiome is readily changeable by diet, antibiotics, pathogenic infections, and host- and environmental-dependent events. The intestine performs key roles of nutrient absorption, tolerance of beneficial microbiota, yet responding to undesirable microbes or microbial products and preventing translocation to sterile body compartments. During homeostasis, the immune system is actively preventing or modulating the response to known or innocuous antigens. Manipulating the microbiota through nutrition, modulating host immunity, preventing pathogen colonization, or improving intestinal barrier function has led to novel methods to prevent disease, but also resulted in improved body weight, feed conversion, and carcass yield in poultry. This review highlights the importance of adding different feed additives to the diets of poultry in order to manipulate and enhance health and productivity of flocks.

Propionic Acid and Sodium Benzoate Affected Biogenic Amine Formation, Microbial Community, and Quality of Oat Silage.

Investigating the microbial communities and biogenic amine (BA) formation in silage is of vital for improving the quality and safety of oat silage. The present study evaluated the effects of propionic acid (P) and sodium benzoate (SB) on the quality properties, microbial communities, and BA formation in oat silage. Oat was harvested at boot stage and ensiled using P and SB as additives in mini silos, followed by 14 days of aerobic exposure. The results showed that P and SB improved fermentation quality of oat silage, increased the lactic acid content, and decreased pH value and ammonia nitrogen content. Putrescine, cadaverine, and tyramine were the dominant BAs in oat silage; spermidine and spermine were not detected. The control silage had the highest content of total biogenic amine (TBA, 2506.7 mg kg–1 DM), and decreased by 51.1 and 57.7% after adding P and SB, respectively. Moreover, a lower putrescine, cadaverine, and tyramine content and undesirable microbes, such as Caproiciproducens, Stenotrophomonas, Herbinix, and Enterobacter genera, were observed in P and SB silages, which was beneficial for oat silage quality. The fungal community of P silage was dominated by Monascus fuliginosus, and the temperature, pH and ammonia nitrogen content increased after exposure to air. Sedimentibacter, Herbinix, Caproiciproducens, Enterobacter, and Escherichia-Shigella were found to be positively correlated with BA formation in oat silage. Overall, P and SB effectively inhibit the undesirable microbes and BA formation in oat silage, the P silage exhibited lower aerobic stability than the SB silage.

Probiotic Characteristics of Ligilactobacillus salivarius AS22 Isolated from Sheep Dung and Its Application in Corn-Fox Tail Millet Silage

The forage crops corn (Zea mays) and foxtail millet (Panicum italicum L.) are widely used as animal feed because of their high nutritive values. The ensiling of corn and foxtail millet is often associated with the growth of undesirable microbes, which cause severe loss of dry matter content during the storage periods. The selection of suitable Ligilactobacillus species for corn-fox tail millet silage production can improve the quality. In this study, we aimed to select potent lactic acid bacteria (LAB) from sheep dung and analyses their biological application such as probiotic features, antimicrobial activities and fermentation capability of silage. A total of nine Lactobacillus strains were inoculated in MRS medium to evaluate lactic acid concentration. The isolated strain, Ligilactobacillus salivarius AS22, produced a higher lactic acid level (40.2 ± 2.2 µg/mL) with high growth rates (2.24 ± 0.12 OD at 600 nm) compared to other strains. The silage treated with inoculant (L. salivarius AS22) decreased the pH value (p < 0.05) and enhanced lactic acid production (p < 0.05) than the control at ensiled silages. LAB inoculated silage had reduced numbers of fungal colonies than control (p < 0.05). In conclusion, the addition of L. salivarius AS22 improved the quality of whole corn and foxtail millet silages with significant probiotic potential.

Emerging Non-Thermal Technologies as Alternative to SO2 for the Production of Wine.

SO2 is an antioxidant and selective antimicrobial additive, inhibiting the growth of molds in the must during the early stages of wine production, as well as undesirable bacteria and yeasts during fermentation, thus avoiding microbial spoilage during wine production and storage. The addition of SO2 is regulated to a maximum of 150–350 ppm, as this chemical preservative can cause adverse effects in consumers such as allergic reactions. Therefore, the wine industry is interested in finding alternative strategies to reduce SO2 levels, while maintaining wine quality. The use of non-thermal or cold pasteurization technologies for wine preservation was reviewed. The effect of pulsed electric fields (PEF), high pressure processing (HPP), power ultrasound (US), ultraviolet irradiation (UV), high pressure homogenization (HPH), filtration and low electric current (LEC) on wine quality and microbial inactivation was explored and the technologies were compared. PEF and HPP proved to be effective wine pasteurization technologies as they inactivate key wine spoilage yeasts, including Brettanomyces, and bacteria in short periods of time, while retaining the characteristic flavor and aroma of the wine produced. PEF is a promising technology for the beverage industry as it is a continuous process, requiring only microseconds of processing time for the inactivation of undesirable microbes in wines, with commercial scale, higher throughput production potential.

Probiotic potential of commercial dairy-associated protective cultures: In vitro and in vivo protection against Listeria monocytogenes infection

Protective bacterial cultures (PCs) are commercially available to producers to control undesirable microbes in foods, including foodborne pathogens such as Listeria monocytogenes. They are generally recognized as safe for consumption and many are capable of producing bacteriocins. Yet their potential to act as probiotics and confer a health benefit on the host is not known. This study investigated the ability of three commercial PCs to survive human gastrointestinal conditions and exert anti-infective properties against L. monocytogenes. Counts of two PCs of Lactiplantibacillus plantarum remained unchanged after exposure to simulated gastrointestinal conditions, whereas counts of the PC Lactococcus lactis subsp. lactis were reduced by 5.3 log CFU/mL. Cultures of Lactiplantibacillus plantarum and Lactococcus lactis subsp. lactis adhered to human Caco-2 epithelial cells at ∼ 6 log CFU/mL. This pretreatment reduced subsequent L. monocytogenes adhesion and invasion by 1–1.6 log CFU/mL and 3.8–4.9 log CFU/mL, respectively, compared to control. L. monocytogenes-induced cytotoxicity was also reduced from 29.1% in untreated monolayers to ∼ 8% in those treated with PCs. Pretreatment of Caco-2 monolayers with Lactococcus lactis subsp. lactis and one PC of Lactiplantibacillus plantarum reduced L. monocytogenes translocation by ≥ 1.2 log CFU/mL compared to control (≥ 94.5% inhibition). All PCs significantly reduced DextranFITC permeability through Caco-2 monolayers to approximately half that of control. Pretreatment with PCs also reduced L. monocytogenes-induced mortality in Caenorhabditis elegans. These findings demonstrate the potential for commercially produced PCs to exert probiotic effects in the host through protection against L. monocytogenes infection, thus providing an additional benefit to food safety beyond inhibiting pathogen growth, survival, and virulence in foods.

Application and Future Prospective of Lactic Acid Bacteria as Natural Additives for Silage Production—A Review

Ensiling is one of the essential processes to preserve fodder with high nutrients and microbiological quality. The forages before ensiling have a limited number of bacteria associated with the controlled fermentation process. Undesirable microbes can grow in silages when there is not efficient fermentation. Such kinds of microbes might cause pathogenic or toxic compounds that affect animal and human health. Therefore, it is necessary to inoculate potent starter cultures. Lactic acid bacteria’s (LABs) have been considered the most prominent microbial additives used to improve the quality of silage. Currently, LABs have been used in modern and sustainable agriculture systems due to their biological potential. Recently, many scientists have increased their focus on developing nutrient-rich animal feed from forages with LAB. This current review focuses on issues related to forage preservation in the form of silages, how undesirable microbes affect the fermentation process, the critical role of LAB in silage production, and the selection of potent LABs to effectively control unwanted microbial growth and promote those which favor animal growth.

Microbial Composition of Fermented Korean Soy Paste (Doenjang) Prepared by Adding Different Herbs during Fermentation

The microbiota involved in Korean soy paste (doenjang) fermentation are the key factors determining its quality aspects. In this study, doenjang was prepared by adding three different herbs (Peppermint, Korean mint, and Coriander), and their effect on the microbiota composition was evaluated by 16S rRNA metagenomic analyses. The β-diversity statistics indicated clear distinctions in the doenjang microbiota after the addition of herbs. A microbial composition analysis revealed that Tetragenococcus was among the dominant genera in the four doenjang groups, with a relatively higher abundance in the Korean mint group. In the Peppermint and Korean mint doenjang groups, the levels of undesirable microbes, such as opportunistic pathogens belonging to the genera Sphingobacterium and Pantoea, were significantly reduced. Additionally, other desirable microbes that are known to exhibit beneficial properties and produce bioactive compounds, such as Saccharopolyspora and Buttiauxella, were present at significantly higher levels. Significant negative correlations between members of the Bacillaceae and Halomonadaceae, Lactobacillaceae and Tissierellaceae, and the Lacobacillaceae and Erwiniaceae families were observed, indicating possible antagonistic relationships. Taken together, our results demonstrated that the incorporation of herbs, particularly Peppermint and Korean mint, during doenjang fermentation resulted in significant shifts in the microbial composition and could be utilized for beneficial effect on its fermentation.

Inhibitory effect of tannin extract from Acacia bark (Acacia mangium Willd.) against gastro-intestinal pathogenic bacteria

Acacia (Acacia mangium Willd) is a fast growing tree species that widely found in Indonesia. Acacia bark contains a number of secondary metabolites such as tannin, saponin and flavonoid that may inhibit the growth of undesirable microbes incuding the pathogenic ones. The purpose of this research was to evaluate the antimicrobial activity of tannin extract obtained from Acacia bark against common pathogenic bacteria species present in the gastro-intestinal tract of livestock, i.e., Salmonella typhimurium and Eschericia coli as Gram negative bacteria. The disc diffusion method was employed for assessing the antimicrobial activity of Acacia tannin extract. Treatments consisted of negative control (NC), positive control by using chloramphenicol (PC), Acacia tannin extract at two concentrations, i.e., 1% (AT1) and 2% w/v (AT2), and commercial chestnut tannin at 1% (CT1) and 2% w/v (CT2). Data were analyzed by using analysis of variance and followed by a post-hoc test namely Duncan’s multiple range test. Results showed that the inhibitory diameters formed on the activity assay of AT in the form powder, liquid and CT with concentration of 2% against Salmonella typhimurium bacteria were 17.3, 7 and 16 mm, respectively. Inhibitory diameters of AT powder, AT liquid and CT against Eschericia coli bacteria were 17.3, 0 and 17 mm, respectively. The AT powder resulted in a higher inhibition of both pathogenic bacteria species than that of liquid form (P<0.05), whereas its inhibitory effect was similar to commercial CT. In conclusion, 2% AT can be used to inhibit the growth of Salmonella typhimurium and Eschericia coli bacteria in which its magnitude of inhibition is comparable with commercial tannin extract from chestnut.