Mixed Culture Of Bacteria Research Articles

Light intensity defines growth and photopigment content of a mixed culture of purple phototrophic bacteria.

Purple bacteria (PPB), anoxygenic photoorganoheterotrophic organisms with a hyper-versatile metabolism and high biomass yields over substrate, are promising candidates for the recovery of nutrient resources from wastewater. Infrared light is a pivotal parameter to control and design PPB-based resource recovery. However, the effects of light intensities on the physiology and selection of PPB in mixed cultures have not been studied to date. Here, we examined the effect of infrared irradiance on PPB physiology, enrichment, and growth over a large range of irradiance (0 to 350 W m-2) in an anaerobic mixed-culture sequencing batch photobioreactor. We developed an empirical mathematical model that suggests higher PPB growth rates as response to higher irradiance. Moreover, PPB adapted to light intensity by modulating the abundances of their phototrophic complexes. The obtained results provide an in-depth phylogenetic and metabolic insight the impact of irradiance on PPB. Our findings deliver the fundamental information for guiding the design of light-driven, anaerobic mixed-culture PPB processes for wastewater treatment and bioproduct valorization.

Synergistic enhancement of biohydrogen production by supplementing with green synthesized magnetic iron nanoparticles using thermophilic mixed bacteria culture

The production of biohydrogen can be improved by focusing on the nutrients needed by fermentative bacteria like iron. Iron reacts with the [Fe-Fe]-hydrogenase enzyme within the mixed bacteria culture for optimum hydrogen release. Iron nanoparticles (NPs) are attractive due to its unique properties and high reactivity. It can be produced through green synthesis, a more eco-friendly and relatively lower cost process, by using iron salt as precursor and green coconut shell extracted by deep eutectic solvent (DES) as reducing agent. The coconut shell extract consists of phytochemicals that help in producing polydisperse magnetic iron oxide nanoparticles at ∼75 nm in size. The addition of optimum concentration of 200 mg Fe/L magnetic iron NPs resulted in the maximum cumulative hydrogen production, glucose utilization and hydrogen yield of 101.33 mL, 9.12 g/L and 0.79 mol H2/mol glucose respectively. Furthermore, the kinetic analysis on Gompertz model using the optimum magnetic iron NPs concentration showed that the hydrogen production potential (P) and hydrogen production rate (Rm) increased to 50.69 mL and 3.30 mL/h respectively and the lag phase time reduced about 7.12 h as compared with the control experiment (0 mg Fe/L). These results indicated the positive effects of magnetic iron NPs supplementation on fermentative biohydrogen production of mixed bacteria culture and proved the feasibility of adding the magnetic iron NPs as the micronutrient for enhancement of such hydrogen production system.

Q-PCR Methodology for Monitoring the Thermophilic Hydrogen Producers Enriched from Elephant Dung

This study aims to create a quantitative polymerase chain reaction (q-PCR) methodology for monitoring the hydrogen-producing mixed cultures enriched from elephant dung using alpha-cellulose as a carbon source through five generations of repetitive sub-culture. The enriched thermophilic mixed cultures from the fifth cultivation cycle gave the highest hydrogen yield of 170.3 mL H2/g cellulose and were used to generate hydrogen from sawdust. Clostridium sp. and Thermoanaerobacterium sp. were the dominant bacteria in thermophilic mixed cultures with high hydrogen yield, according to polymerase chain reaction-denatured gradient gel electrophoresis (PCR-DGGE). q-PCR primers Chis150F and ClostIR, TherF and TherR, and BacdF and BacdR were developed to amplify the 16S rRNA genes of Clostridium sp., Thermoanaerobacterium sp., and Bacillus sp., respectively, for the quantification of hydrogen-producing bacteria in biohydrogen fermentation. Similar q-PCR analysis of Clostridium sp., Thermoanaerobacterium sp., and Bacillus sp. 16S rRNA gene amplification during hydrogen production from cellulose and sawdust revealed increasing gene copy number with time. The molecular approaches developed in this study can be used to monitor microbial communities in hydrogen fermentation processes efficiently.

Smart capsule for targeted proximal colon microbiome sampling

The gastrointestinal (GI) tract, particularly the colon region, holds a highly diverse microbial community that plays an important role in the metabolism, physiology, nutrition, and immune function of the host body. Accumulating evidence has revealed that alteration in these microbial communities is the pivotal step in developing various metabolic diseases, including obesity, inflammatory bowel disease (IBD), and colorectal cancer. However, there is still a lack of clear understanding of the interrelationship between microbiota and diet as well as the effectiveness of chemoprevention strategies, including pre and probiotic agents in modifying the colonic microbiota and preventing digestive diseases. Existing methods for assessing these microbiota-diet interactions are often based on samples collected from the feces or endoscopy techniques which are incapable of providing information on spatial variations of the gut microbiota or are considered invasive procedures. To address this need, here we have developed an electronic-free smart capsule that enables site-specific sampling of the gut microbiome within the proximal colon region of the GI tract. The 3D printed device houses a superabsorbent hydrogel bonded onto a flexible polydimethylsiloxane (PDMS) disk that serves as a milieu to collect the fluid in the gut lumen and its microbiome by rapid swelling and providing the necessary mechanical actuation to close the capsule after the sampling is completed. The targeted colonic sampling is achieved by coating the sampling aperture on the capsule with a double-layer pH-sensitive enteric coating, which delays fluid in the lumen from entering the capsule until it reaches the proximal colon of the GI tract. To identify the appropriate pH-responsive double-layer coating and processing condition, a series of systematic dissolution characterizations in different pH conditions that mimicked the GI tract was conducted. The effective targeted microbial sampling performance and preservation of the smart capsule with the optimized design were validated using both realistic in vitro GI tract models with mixed bacteria cultures and in vivo with pigs as an animal model. The results from 16s rRNA and WideSeq analysis in both in vitro and in vivo studies showed that the bacterial population sampled within the retrieved capsule closely matched the bacterial population within the targeted sampling region (proximal colon). Herein, it is envisioned that such smart sampling capsule technology will provide new avenues for gastroenterological research and clinical applications, including diet-host-microbiome relationships, focused on human GI function and health. Statement of significanceThe colonic microbiota plays a major role in the etiology of numerous diseases. Extensive efforts have been conducted to monitor the gut microbiome using sequencing technologies based on samples collected from feces or mucosal biopsies that are typically obtained by colonoscopy. Despite the simplicity of fecal sampling procedures, they are incapable of preserving spatial and temporal information about the bacteria through the gastrointestinal (GI) tract. In contrast, colonoscopy is an invasive and impractical approach to frequently assess the effect of dietary and therapeutic intake on the microbiome and their impact on the health of the patient. Here, we developed a non-invasive capsule that enables targeted sampling from the ascending colon, thereby providing crucial information for disease prediction and monitoring.

Chemical Composition of Kombucha

Kombucha is a fermented sweetened tea with a mixed fermenting culture of yeast and acetic acid bacteria. While the history of kombucha is not completely clear, it is now available around the world and has shown an increase in availability and demand in the United States market. The proponents of kombucha consumption tout the varied health benefits it can provide. The final kombucha flavor and composition is a function of both the initial tea used and the fermentation process. While the ascribed benefits are varied and numerous, the number of direct studies has been limited. This review focuses on the current state of understanding of the chemical composition and the potential health effects both positive and negative reported in the literature.

Production of Single-Cell Protein from Fruit Peel Wastes Using Palmyrah Toddy Yeast

Single-cell protein (SCP) from agro-waste material has gained increased attention in the recent past as a relatively cheap and alternative protein source to meet the nutritional demand generated by the fast-growing population. Furthermore, bioconversion of these wastes into SCP such as value-added products reduce the environmental-related issues. In this study, locally available pineapple (Ananas comosus), watermelon (Citrullus lanatus), papaya (Carica papaya), sour orange (Citrus medica), banana (Musa acuminata) and mango (Mangifera indica) peel wastes were investigated for their suitability to produce SCP using palmyrah (Borassus flabellifer) toddy carrying natural mixed yeast and bacteria culture under liquid state fermentation system. Moreover, this study attempted to select the best substrate and the optimized process condition for SCP production to increase the protein yield. The physicochemical properties of selected fruit peels were analyzed. The sterilized peel extracts (10%, v/v) were inoculated with 5 mL of palmyrah toddy and allowed to ferment in a shaking incubator at 100 rpm for 48 h in triplicate At the end of fermentation, the sediments were collected by centrifugation at 1252× g, oven-dried, and the dry weight was taken to determine the protein content. The biomass yield ranged from 5.3 ± 0.6 to 11.7 ± 0.8 g/L, with the least biomass yield being observed with watermelon peels while the maximum yield was observed with papaya peels. Papaya peel generated a significantly higher (p < 0.05) amount of protein (52.4 ± 0.4%) followed by pineapple (49.7 ± 1.3%), watermelon (45.2 ± 0.7%), banana (30.4 ± 0.6%), sour orange (29.5 ± 1.2%) and mango (24.6 ± 0.2%) peels. The optimum condition for the fermentation of papaya waste was pH 5.0, 25 °C, and 24 h. Nucleic acid reduction treatment significantly reduces dry weight and protein content of biomass. It can be concluded that papaya peel waste is a suitable substrate for protein-rich cell biomass production using the natural toddy mixed culture of palmyrah.

Fermentation performance, nutrient composition, and flavor volatiles in soy milk after mixed culture fermentation

In this study, a mixed culture of lactic acid bacteria (LAB) and kombucha bacteria was used to ferment soy milk. The microbial composition and the rheological properties, isoflavones, vitamins, and volatile flavor substances were quantitatively analyzed during fermentation. The fermentation process could significantly change the viscoelastic rheological properties of soy milk. Most of the isoflavone glycosides were hydrolyzed to aglycones by β-glucosidase produced during fermentation. The isoflavone content increased significantly as fermentation progressed. B vitamins content increased significantly, riboflavin content increased from 117.44 to 162.58 µg/g dry weight (dw), and cobalamin content, not detected before fermentation, increased to 106.73 µg/g dw. Microbial fermentation promoted protein aggregation and decreased the fat content of soy milk. After fermentation, the content of characteristic flavor substances in soybean, such as hexanal, was significantly reduced, and some new flavor compounds were generated from the fermentation-derived alcohols, esters, and acids. The combination of LAB and kombucha bacteria can enrich the taste and significantly enhance the nutritional properties and antioxidant capacity of fermented soy milk and provides a new idea for the research and development of fermented soy milk and its related plant-based fermented products.

Electron donor addition for stimulating the microbial degradation of 1,4 dioxane by sequential batch membrane bioreactor: A techno-economic approach

The presence of 1,4 dioxane in wastewater is associated with severe health and environmental issues. The removal of this toxic contaminant from the industrial effluents prior to final disposal is necessary. The study comprehensively evaluates the performance of sequential batch membrane bioreactor (MBR) for treating wastewater laden with 1,4 dioxane. Acetate was supplemented to the wastewater feed as an electron donor for enhancing and stimulating the microbial growing activities towards the degradation of 1,4 dioxane. The removal efficiency of 1,4 dioxane was maximized to 87.5 ± 6.8% using an acetate to dioxane (A/D) ratio of 4.0, which was substantially dropped to 31.06 ± 3.7% without acetate addition. Ethylene glycol, glyoxylic acid, glycolic acid, and oxalic acid were the main metabolites of 1,4 dioxane biodegradation using mixed culture bacteria. The 1,4 dioxane degrading bacteria, particularly the genus of Acinetobacter, were promoted to 92% at the A/D ratio of 4.0. This condition encouraged as well the increase of the main 1,4 dioxane degraders, i.e., Xanthomonadales (12.5%) and Pseudomonadales (9.1%). However, 50% of the Sphingobacteriales and 82.5% of Planctomycetes were reduced due to the inhibition effect of the 1,4 dioxane contaminate. Similarly, the relative abundance of Firmicutes, Verrucomicrobia, Chlamydiae, Actinobacteria, Chloroflexi, and Nitrospirae was reduced in the MBR at the A/D ratio of 4.0. The results derived from the microbial analysis and metabolites detection at different A/D ratios indicated that acetate supplementation (as an electron donor) maintained an essential role in encouraging the microorganisms to produce the monooxygenase enzymes responsible for the biodegradation process. Economic feasibility of such a MBR system showed that for a designed flow rate of 30 m3∙d−1, the payback period from reusing the treated wastewater would reach 6.6 yr. The results strongly recommend the utilization of mixed culture bacteria growing on acetate for removing 1,4 dioxane from the wastewater industry, achieving dual environmental and economic benefits.

Моделирование нечеткой логики для управления процессом бактериального окисления концентратов в реакторах с мешалкой

Множественность химических, биологических, технологических параметров и нелинейная зависимость при извлечении металлов в средах бактериального окисления усложняют математическое моделирование этих систем. Данное исследование было проведено с целью обеспечить управление извлечением золота и железа из флотоконцентрата в биореакторе с мешалкой с использованием модели нечеткой логики. Опыты проводились в присутствии смешанной культуры ацидофильных бактерий (Lactobacillus acidophilus) при 42°С и смешанной культуры умеренно термофильных бактерий при 48°С. Входными переменными были: метод операции, тип бактерий и время. Извлеченное золото и железо являлись выходными данными. Связь между указанными входными данными и выходными данными была обеспечена с помощью разработанных правил «ЕСЛИ-ТО». Полученная нечеткая модель показала удовлетворительный прогноз извлечения золота и железа и имела хорошую корреляцию экспериментальных данных с R-квадратом (более 0,97). Результаты исследования показали, что нечеткая логика представляет собой мощный и надежный инструмент для прогнозирования нелинейных и изменяющихся во времени процессов бактериального окисления.

Formulation of Soil Beneficial Microbes Solid Inoculant for Controlling Nematode in Coffee

Plant Growth Promoting Rhizobacteria Pseudomonas and Bacillus are well known biofertilizer due to their ability for solubilizing inorganic phosphate and producing phytohormones in soil. However, their potential to decreased diseases incidence caused by Pratylenchus coffeae has been documented. The objective of this laboratory experiment was to formulate solid biofertilizer contained Pseudomonas diminuta and Bacillus subtilis. The laboratory experiments consisted of three-step experiment: 1) selection of the molasses-based liquid media for P. diminuta and B. subtilis growth, 2) organic liquid inoculant formulation and 3) organic carrier-based inoculant formulation. The population of both bacteria in all steps was count by serial dilution plate method with specific medium. The result verifeid that cell density of P. diminuta and B. subtilis in liquid culture with 2% molasses were higher than cell count in the culture contained 4% molasses. Bagasse-based carrier inoculated with liquid culture of mixed bacteria has higher bacterial count compared to manure-based carrier. After 90-day incubation, bagasse-based solid inoculant maintained P. diminuta and B. subtilis density up to 108 CFU/mL and the acidity of solid inculaant was about neutral. The bacterial count and acidity of solid inoculant agreed with Indonesian standard for solid biofertilizer

Use of GC-IMS for detection of volatile organic compounds to identify mixed bacterial culture medium

In order to explore the possibility to identify common wound infection bacteria in mixed culture with gas chromatograph-ion migration spectroscopy (GC-IMS), the headspace gas of single and mixed cultures of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were detected and analyzed by GC-IMS system. The bacteria were cultured in thioglycolate medium tubes then transferred to the sampling bottles (indirect method), or directly cultured in the sampling bottles (direct method) to allow accumulation of volatile compounds and facilitate automation. The specific microorganism volatile organic compounds (mVOCs) of the three bacteria were obtained. Some of them have been known to certain substance, for example, ethanol, isoamyl acetate, Phenylacetaldehyde, 2-heptanone etc., while others have not. Principal component analysis (PCA) showed that a higher separability can be achieved with direct method than indirect method. This work indicated that it is possible to identify compound bacteria by detecting specific mVOCs with GC-IMS, and the specific mVOCs should be medium-dependent.

Formulation, Processing and Characterization of Fermented Probiotic Mango Juice Using Selected Starter Cultures

Probiotics are live microorganisms added to food products to confer health benefits such as gut health, cancer protection and improved immunity when consumed. Fruits juices are considered as potential channels for delivering probiotics as they contain essential nutrients and low pH suitable for the growth of probiotics. The study was undertaken to formulate, process and characterize fermented probiotic mango fruit juice using three different mixed lactic acid bacteria cultures: Abt-5® culture (Streptococcus thermophillus, Bifidobacterium and Lactobacillus acidophilus); Fiti® culture (Lactobacillus rhamnosus GR-1) and Yo-mix® culture (Streptoc.occus thermophillus and Lactobacillus delbruikii ssp bulgaricus). The viability of the cultures was also assessed. The mango juice was formulated using mango pulp to water ratios of 100:0, 25:75, 50:50 and 75:25 (v/v) and adjusted to 17° brix by adding cane sugar. The formulated mango juices were pasteurized at 90 °C for 1 minute and cooled to 10 °C. Sensory evaluation was carried out to determine the most preferred formulation of the fruit juice before fermentation. The preferred mango juice samples were cooled to 402 °C and incubated with the three different mixed bacteria cultures (1 g/l) for 0, 12, 16, 24, 36, 48 and 72 hours. The final product stored at 4 °C. Analysis for sensory evaluation, culture viability, pH, total soluble solids (TSS) and total titratable acidity (TTA) was done. The 50:50 ([mango pulp: water) mango fruit juice formulation was significantly different (p<0.05) from the other samples in consistency and was rated the best in overall acceptability. There was general increase in cell count in all cultures with mango juice fermented with Lactobacillus rhamnosus GR-1 for 48 hours recording the highest viable cell count of log10 9.14 CFU/ml. Highest pH decrease was observed in 50:50 formulation with significant (p<0.05) increase in TTA from 0.15% to 0.69% using Lactobacillus rhamnosus GR-1 within 72 hours. Subsequently, the TSS decreased from 17° brix to 14.47° brix. The study showed that the three mixed were able to utilize nutrients present in the formulated mango juice during fermentation as demonstrated by decrease in pH and TSS. The study therefore recommends that further research should be done on the probiotic fermented mango juice to determine the change in physco-chemical characteristics and culture viability during storage.

Single Cell Proteins production from food processing effluents and digestate

The increase in human population determines a higher proteins request to sustain the feed demand for animals and aquaculture. Single Cell Proteins (SCPs) consist of mixed protein from pure and mixed culture of bacteria, fungi, algae, and yeast, which are grown and harvested to accomplish the food requirement of human and animals. This work investigated the production of Saccharomyces cerevisiae to be used as SCPs for animal feeding. The effluent of candies production process, rich in sugars, about 40 g/L, and agricultural digestate rich in nitrogen and other macro and micronutrients, were used for the yeast's growth. Preliminary batch tests demonstrated that aerobic conditions optimized the biomass growth. Then, continuous aerobic tests were conducted at different dilution rates. The dilution rate of 0.50 d−1, corresponding to a hydraulic retention time of 2 days, optimized both the biomass productivity of 0.25 g/L per day and the protein content of 28% w/w. The analysis of the aminoacidic profile demonstrated that obtained SCPs could be used as an integrator of feed for fish and monogastric animals. On the contrary, they were not suitable for pet feed as all the amino acids concentrations were lower than required standards. These results suggested that anaerobic digesters in the agricultural sector can be transformed into small biorefineries for microbial protein production.

유산균 복합배양 양배추 발효물의 항염증 효과

In this study, we investigated the anti-inflammation effect of cabbage (Brassica oleracea L var. capitata) fermented with a mixed culture of lactic acid bacteria (FCMC) and elucidated the underlying mechanism. The mixed culture included Lactobacillus plantarum and L. acidophilus. The cell viability of RAW264.7 macrophages were confirmed by MTT assay, and the results revealed no toxicity following treatment with FCMC at concentrations of up to 1,000 μg/mL. The anti-inflammatory effect of FCMC was evaluated by stimulating RAW264.7 macrophages with lipopolysaccharide (LPS) to induce the production of inflammation-related factors, which were measured by an nitric oxide (NO) assay, enzyme-linked immunosorbent, and Western blot. FCMC dose-dependently inhibited the production of NO, PGE2, and the pro-inflammatory cytokines IL-1β and TNF-α in LPS-stimulated RAW264.7 macrophages without any cytotoxicity. FCMC also reduced the protein expression levels of iNOS and COX-2 and inhibited the nuclear translocation of NF-κB and degradation of IκB in the LPS-stimulated cells. These results collectively suggest that FCMC may suppress the inflammatory reaction in LPS-stimulated RAW264.7 macrophages by regulating the NF-κB signaling pathway and function as an anti-inflammatory material.

Mineralization of pyrene (polycyclic aromatic hydrocarbon) in clay soil supplemented with animal organic carbon source

Biostimulation of polycyclic aromatic hydrocarbons (PAHs) is a major concern in the environment due to their toxic nature and ubiquitous occurrence. The study aimed to determine the best animal supplement of organic carbon source (cow dung, goat dung, pig dung and poultry (fowl droppings) and indigenous microbes capable of mineralizing pyrene in clay soil. Clay soil sample was collected from the top surface soil (0 - 15cm) in Ikpoba River and upper Lawani river bank, both in Benin City with the aid of stainless steel trowel and gloved hands and stored in a polyethylene bag. The isolation and identification process were evaluated by staining method, microscopic examination and biochemical tests. The degradation experiment was conducted in bioreactors and supplemented cow dung, pig dung, goat dung and fowl droppings were added in varying amounts of 25g/l, 50g/l, 75g/l and 100g/l. The potential effects of animal organic carbon as nutrient supplements to enhance mineralization of pyrene were investigated. The rates of mineralization of pyrene were studied for a remediation period of 35days at room temperature of about 25°C. Results obtained from microbial isolation showed that B. substilis and A. niger were the most populated in the soil and were therefore selected. The degradation experiment showed that mixed culture of B. substilis and A. niger using 50g/l supplement with the dungs and droppings gave the highest percentage degradation with fowl droppings 98.3%, pig dung 98.1%, goat dung 97.8%, and cow dung 97.7%. The least degradation was observed in supplement with 100g/l in a single culture of A. niger with fowl droppings yielded 64.5% degradation, pig dung 63.8%, goat dung 63.7% and cow dung 62.7%. The overall results of the study showed that 50g/l of animal wastes supplement in the ratio of 1:4 with pyrene contaminated soils are most effective in degradation processes. Also the mixed culture of bacteria and fungi enhanced pyrene mineralization and degradation more than single culture.

Ispitivanje fitostimulatornog delovanja bakterijskih sojeva tokom gajenja uljanog lana i crnog kima

In order to examine the influence of plant growth stimulating bacteria, which belong to the genus Streptomices sp., Paenibacillus sp. and Hymenibacter sp., on the yield and seed quality of linseed and black cumin, as well as on the morphological characteristics of these plants, a two-year field experiments were conducted. Soil treatment with a mixed culture of bacteria of different concentrations was applied during the sowing of plants. Before sowing, the influence of individual strains on the germination index of linseed and black cumin was examined. Based on the results presented in the paper, the strains CKS1 - Paenybacillus chitinolyticus, CKS3 - Hymenobacter sp., and CKS7 - Streptomyces fulvissimus, gave germination index values GI over 100% in linseed, within all tested concentrations, while in black cumin, such an effect was shown only by strain CKS7. The positive effect of the bacterial preparation in both examined plant species was recorded by measuring the yield of seeds per hectare treated with a lower concentration of the bacterial preparation compared to the corresponding untreated samples (control sample). A significant difference was recorded by measuring the number of cocoons in samples of treated linseed compared to untreated ones, as well as the mass of roots of both treated plant species. Also, the highest overall germination compared to the control was achieved by the linseed variant L2 in the treatment with a lower concentration of bacteria of 98.3±1.4%.

Investigation on the elimination of yeasty flavour in yeast extract by mixed culture of lactic acid bacteria and yeast

SummaryYeast extract (YE) is a kind of umami additives used in fermented condiments, it also has special yeasty flavour (YF), which is not widely accepted by some consumers. In this paper, the technology of mixed microbial transformation was applied to eliminate or cover up YF during mixed fermentation. FG10, which is produced by Hubei Angel Yeast Co. Ltd, is a kind of YE that has the distinctive YF and has been applied to the market. It had good sensory evaluation after 6 h with Saccharomycopsis fibuligera and Lactococcus lactis. At 6 h, compared with single fermentation, the number of bacteria of L. lactis was enhanced by 34.28%, and the number of bacteria of S. fibuligera was reduced by 47.93%. The yeasty flavoured substances propionic acid and butyric acid were completely removed. The result of GC‐MS showed that acetal, phenyl acetaldehyde, 2,4‐dimethylbenzaldehyde, benzaldehyde, isoamyl alcohol, 5‐methyl‐2‐furan methanol, phenylethanol were generated or increased. Furthermore, the amino acids of YE were significantly different after fermentation by different microorganisms (P < 0.05), The flavour compounds and amino acids in YE before and after fermentation had closely correlation (r = 0.94), the consumption of amino acids in mixed fermentation promoted the variety of corresponding flavour compounds, which boosted the formation of free YF YE. In addition, taste substances lactic acid generated 6.27 ± 0.115 g L−1 and nucleotides improved 15.05%, which were beneficial to natural YF free seasoning with YE as raw material.

The effects of Pinus brutia bark extract on pure and mixed continuous cultures of rumen bacteria and archaea, and fermentation characteristics in vitro

The aim of the study was to investigate the effects of Pinus brutia bark extract, which is rich in polyphenolic compounds of tannins, on both pure and mixed continuous cultures of rumen bacteria and archaea, as well as on rumen fermentation characteristics in vitro. Antimicrobial susceptibility assay with pure cultures was carried out in an anaerobic chamber. Pinus brutia bark extract exhibited a potential inhibitor activity (P<0.05) against pure cultures of Ruminococcus flavefaciens, Eubacterium ruminantium, and Methanobacterium formicicum while a growth stimulatory effect (P<0.05) was observed for Ruminoccocus albus, Butyrivibrio fibrisolvens, and Streptococcus bovis. Pinus brutia bark extract only had a potential inhibitor effect (P<0.05) on R. albus at the highest dose (1200 µg/mL). Pinus brutia bark extract also stimulated (P<0.05) the growth of pure cultures of Fibrobacter succinogenes, while it did not affect Megasphaera elsdenii, except at the highest dose. The effects of two doses (75 and 375 mg/L) of P. brutia bark extract on in vitro mixed cultures and rumen fermentation parameters were determined by the rumen simulation technique (Rusitec). Supplementation with P. brutia bark extract led to a quadratic decrease (P<0.05) in the cell numbers of R. flavefaciens. Production of total and individual short chain fatty acids (SCFA), acetate to propionate ratio (C2/C3), total protozoa, ruminal pH, and dry matter digestibility (DMD) did not change in the presence of P. brutia bark extract. Supplementation with both doses of P. brutia bark extract decreased (P<0.05) the ammonia-N concentrations. Ammonia-N concentration was lowest in the high-supplemented group (P<0.05). As a conclusion, inhibitory effects of P. brutia bark extract on some species in the pure cultures were in the same direction as with mixed ruminal cultures, while stimulatory effects disappeared. The lack of inhibitory effects on protozoa and on a large number of Gram-positive rumen bacteria in the mixed cultures suggests that its mechanism of action is not exactly similar to antibiotics. Although P. brutia bark extract did not alter ruminal SCFA, it could have potential to improve ruminal protein utilization without depressing rumen microbial fermentation.

Integrating mechanistic and deep learning models for accurately predicting the enrichment of polyhydroxyalkanoates accumulating bacteria in mixed microbial cultures

The enrichment of polyhydroxyalkanoates (PHA) accumulating bacteria (PAB) in mixed microbial cultures (MMC) is extremely difficult to be predicted and optimized. Here we demonstrate that mechanistic and deep learning models can be integrated innovatively to accurately predict the dynamic enrichment of PAB. Well-calibrated activated sludge models (ASM) of the PAB enrichment process provide time-dependent data under different operating conditions. Recurrent neural network (RNN) models are trained and tested based on the time-dependent dataset generated by ASM. The accurate prediction performance is achieved (R2 > 0.991) for three different PAB enrichment datasets by the optimized RNN model. The optimized RNN model can also predict the equilibrium concentration of PAB (R2 = 0.944) and corresponding time, which represents the end of the PAB enrichment process. This study demonstrates the strength of integrating mechanistic and deep learning models to predict long-term variations of specific microbes, helping to optimize their selection process for PHA production.

Structure-Based Long-Term Biodegradation of the Azo Dye: Insights from the Bacterial Community Succession and Efficiency Comparison

In this study, microbial community dynamics were explored during biological degradation of azo dyes with different chemical structures. The effect of the different molecular structures of the azo dyes was also assessed against the simultaneous removal of color and the bacterial community. Winogradsky columns were inoculated with dewatered sludge and separately fed with six different azo dyes to conduct the sludge acclimatization process, and nine bacterial decolorizing strains were isolated and identified. The decolorization and biodegradation performances of the acclimated system and isolated strains were also determined. Results showed that the bacterial isolates involved in decolorization and the degradation of the azo dyes were mainly associated with the azo dye structure. After 24 h acclimatization at room temperature without specific illumination, immediate decolorization of methyl red (89%) and methyl orange (78%) was observed, due to their simple structure compared to tartrazine (73%). However, after 8 days of acclimatization, methyl red was easily decolorized up to 99%, and about 87% decolorization was observed for orange G (87%), due to its complex chemical structure. Higher degrees of degradation and decolorization were achieved with Pseudomonas geniculate strain Ka38 (Proteobacteria), Bacillus cereus strain 1FFF (Firmicutes) and Klebsiella variicola strain RVEV3 (Proteobacteria) with continuous shaking at 30 °C. The azo dyes with benzene rings were found to be easier to decolorize and degrade with similar microbial communities. Moreover, it seems that the chemical structures of the azo dyes, in a sense, drove the divergent succession of the bacterial community while reducing the diversity. This study gives a deep insight into the feasible structure-based artificial manipulation of bacterial communities and offers theoretical guidance for decolorizing azo dyes with mixed bacteria cultures.