Mixed Culture Of Microorganisms Research Articles

Collaboration of bacterial consortia for biodegradation of high concentration phenol and potential application of machine learning

Mixed culture of microorganisms is an effective method to remove high concentration of phenol in wastewater. At present, it is still a challenge for microorganisms to remove high-concentration phenol from wastewater. In this study, a phenol-degrading consortium was isolated, which could rapidly degrade 1800 mg/L phenol within 30 h, and the highest phenol degradation concentration was 2000 mg/L. Further exploration of how microbial consortium cooperates to promote phenol biodegradation was studied: the core bacteria of the microbial consortium was relatively stable during phenol degradation; the bacteria could improve the adaptability to environment and metabolic ability of phenol, by producing more surfactants and betaine, thereby improving the degradation rate. The determination coefficient (R2) in the machine learning model showed that the back propagation artificial neural network (BP-ANN) can predict the biodegradation of phenol under different conditions, saving time and economic costs. This study explains how microbial consortium cooperates to degrade phenol from the aspects of microbial consortium composition and metabolic analysis, which provides a theoretical basis for mixed culture microorganisms to degrade pollutants.

Isolation and molecular characterization of microorganisms with biofertilizer potential

Biofertilizers are microbial-agro products containing mixed culture of microorganisms that promote plant growth, yield, soil quality and disease control. This study aimed to isolate, identify and screen microorganisms with biofertilizer potentials for application in farms. Soil samples were collected from farmland and waste-dump soils around University of Port Harcourt. The various microorganisms were isolated and estimated using nutrient agar, potato dextrose agar, cetrimide agar and Ashby’s agar. The microorganisms were screened for biofertilizer potentials based on nitrogen fixation, potassium and phosphate solubilization using Pikovskaya media. The results obtained from this study showed that thefarmland soil sample had a total heterotrophic bacterial and fungal counts of 5.045±0.02 and 4.220±0.02 Log10Cfu/gwhile the corresponding values in the waste-dump soil was 4.890±0.30 and 3.505±0.30 Log10Cfu/g respectively. After screening, the microorganisms with biofertilizer potentials were identified as Aspergillus niger, Penicillium chrysogenum, Bacillus cereus, Bacillus licheniformis, Pseudomonas fluorescens and Azotobacter chroococcum. Findings from this study have demonstrated that the microorganisms isolated from the farmland soil were more adept at nitrogen fixation and solubilizing insoluble potassium and phosphate compounds than their counterparts in waste-dump soil. These microorganisms have shown potentials to improve soil fertility and crop productivity in a sustainable way.

Issues about application of bioremediation for cleaning up of contaminated sites

Bioremediation as a cleaning up technology is less predictable and efficient for application on site. An apparent gap is still evident between the laboratory results with pure culture or mixed culture of microorganisms and their biochemical capability including genes and enzymes involved, and the effectiveness at cleaning up the pollutants in soil and sediment on site. Associated issues include the characteristics of the site, ageing of the chemical pollutants and sequestration into soil as one, and activity and competitive of the degradative microorganisms under the actual contaminated conditions of natural environment. Because of these, the favorable conditions for the active growth of degradative microorganisms have not been investigated well enough with the available technology, so a simple inoculation of the pure culture effective under laboratory conditions cannot guarantee an expected efficiency and positive results at on site testing. In addition, the soil or sediment physical and chemical conditions under the natural environment play an important role in the removal or mineralization of organic pollutants, but inadequate attention has been given to these factors involved from ecology. It is the objectives here to bring the attention to the bioavailable concentration of the pollutants and also the active metabolism of the organisms in situ to advance and demonstrate the effective cleaning up of contaminated sites.

Thermodynamics of microbial consortia: Enthalpies and Gibbs energies of microorganism live matter and macromolecules of E. coli, G. oxydans, P. fluorescens, S. thermophilus and P. chrysogenum

Every microorganism represents a biothermodynamic system, characterized by an empirical formula and thermodynamic properties of biosynthesis. Gibbs energy of biosynthesis influences the multiplication rate of a microorganism. In case of a mixed culture (microbial consortia) biosynthesis processes of microbial species are competitive. This is why Gibbs energy of biosynthesis determines the growth in a mixed culture. This paper gives a mechanistic model that explains growth of microorganisms in mixed culture and ability to grow in microbial consortia. Detailed biosynthesis reactions were formulated for the first time for five microorganism species, which include metallic elements. Moreover, thermodynamic properties of live matter and biosynthesis were calculated for the first time for five microorganism species and macromolecules.

Enhanced biodegradation of phenol by microbial collaboration: Resistance, metabolite utilization, and pH stabilization

Mixed culture of microorganisms is an effective method to remove high concentration of phenol from wastewater. Currently, the mechanism of how microorganisms collaborate to enhance the biodegradation of phenol is still a challenge. In this study, the isolated Bacillus subtilis ZWB1 and Bacillus velezensis ZWB2 were co-cultured to enhance phenol biodegradation, and the mechanism of microbial collaboration was further explored. The co-culture of strains could significantly increase the rate (16.7 mg/L·h, 1000 mg/L) and concentration of phenol degradation (1500 mg/L), comparing with mono-culture of ZWB1 (4.2 mg/L·h, 150 mg/L) and ZWB2 (6.9 mg/L·h, 1000 mg/L), among which the highest degraded concentration of phenol for ZWB1 and ZWB2 was 150 and 1000 mg/L. Further, the mechanism of microbial collaboration to enhance phenol biodegradation was raised: the decrease of antioxidant enzymes, and increase of degrading enzymes and surfactants on content after co-culture, assisted the microorganisms in withstanding phenol; Bacillus subtilis ZWB1 used the metabolites of Bacillus velezensis ZWB2 to promote its growth, and further to degrade phenol rapidly; Bacillus subtilis ZWB1 alleviated the damage, which resulted from the pH drop (5.8) of the fermentation broth during phenol degradation that inhibited the growth and degraded ability of Bacillus velezensis ZWB2, making the pH of fermentation broth stable at 7. Metabolic analysis showed that co-culture of strains could produce more alkaline and buffering compounds and pairs, to stabilize pH and reduce the toxicity of acidity on ZWB2, thus increasing the degradation rate. This study explains the mechanism of microbial collaboration on phenol biodegradation from multiple perspectives, especially pH stabilization, which provides a theoretical basis for the degradation of pollutants by co-culture microorganisms.

Screening the Efficacy of a Microbial Consortium of Bacteria and Fungi Isolated from Different Environmental Samples for the Degradation of LDPE/TPS Films

In this study, a screening of the efficacy of a microbial consortium of bacteria and fungi isolated from activated sludge, river sediment, and compost for the degradation of LDPE/TPS was performed. According to the morphological and biochemical characterization, eight bacteria, Bacillus sonorensis, Bacillus subtilis, Lysinibacillus massiliensis, Bacillus licheniformis, Bacillus indicus, Bacillus megaterium, Bacillus cereus, and Pseudomonas alcaligenes, five molds, Aspergillus sp. 1, Aspergillus sp. 2, Trichoderma sp., Rhizopus sp., Penicillium sp., and Alternaria sp., and a yeast, Candida parapsilosis, were identified. The first experiment E1 was inoculated with microorganisms isolated from activated sludge and river sediment, and E2 with microorganisms isolated from compost. In both experiments, different types of polymeric materials, low density polyethylene (E1-1 and E2-1), thermoplastic starch (E1-2 and E2-2), low density polyethylene + thermoplastic starch (E1-3 and E2-3), low density polyethylene + thermoplastic starch + styrene-ethylene-styrene (E1-4 and E2-4) were added. The obtained results, weight loss, SEM, and FTIR analysis showed that the microorganisms in both experiments were able to degrade polymeric materials. The mixed culture of microorganisms in experiments E1-2 and E2-2 completely degraded TPS (thermoplastic starch). The percent weight losses of LDPE, LDPE+20% TPS, and LDPE+20% TPS+SEBS in experiment E1 were 3.3184%, 14.1152%, and 16.0062% and in experiment E2 were 3.9625%, 20.4520% and 21.9277%, respectively. SEM microscopy shows that the samples with a LDPE matrix exhibited moderate surface degradation and negligible oxidative degradation under the given conditions. FTIR/ATR data demonstrate that degradation was more intense in E2 than in E1.

Enhanced Methane Production from Pretreatment of Waste Activated Sludge by Economically Feasible Biocatalysts

Crude hydrolytic extracellular enzymes (CHEEs) generated by a mixed culture of microorganisms during fermentation have a high potential as economically feasible biocatalysts for the hydrolysis of complex organic wastes. This study investigates the feasibility of CHEEs as substitutes for commercial enzymes based on a series of anaerobic batch tests for CH4 production fed by pretreated waste activated sludge (WAS). The results showed that cellulase presented the highest CH4 yield of 99.1 mL·CH4/g·COD of WAS among the samples pretreated with single commercial enzymes, with a yield 34% higher than that of the control sample. A higher diversity of commercial enzymes used in the pretreatment led to higher CH4 production from WAS. The sample pretreated with a mixture of four commercial enzymes (amylase + protease + cellulase + lipase, APCL) presented a CH4 yield of 216.0 mL·CH4/g·COD of WAS. The WAS prepared with CHEEs resulted in a CH4 yield of 211.9 mL·CH4/g·COD of WAS, which is comparable to the performance of the sample pretreated with APCL. The results of the batch tests using pretreated WAS for different APCL concentrations showed that the CH4 yield of WAS pretreated with CHEEs was comparable to the CH4 yield of 0.34 g·APCL/g·COD of WAS.

Water Kefir Grains-Microbial Biomass Source for Carbonaceous Materials Used as Sulfur-Host Cathode in Li-S Batteries.

Nowadays, the use of biomass to produce cathode materials for lithium-sulfur (Li-S) batteries is an excellent alternative due to its numerous advantages. Generally, biomass-derived materials are abundant, and their production processes are environmentally friendly, inexpensive, safe, and easily scalable. Herein, a novel biomass-derived material was used as the cathode material in Li-S batteries. The synthesis of the new carbonaceous materials by simple carbonization and washing of water kefir grains, i.e., a mixed culture of micro-organisms, is reported. The carbonaceous materials were characterized morphologically, texturally and chemically by using scanning electron microscopy, N2 adsorption-desorption, thermogravimetric analysis, X-ray diffraction, and both Raman and X-ray photoelectron spectroscopy. After sulfur infiltration using the melt diffusion method, a high sulfur content of ~70% was achieved. Results demonstrated that the cell fitted with a cathode prepared following a washing step with distilled water after carbonization of the water kefir grains only, i.e., not subjected to any chemical activation, achieved good electrochemical performance at 0.1 C. The cell reached capacity values of 1019 and 500 mAh g-1 sulfur for the first cycle and after 200 cycles, respectively, at a high mass loading of 2.5 mgS cm-2. Finally, a mass loading study was carried out.

Microbial strategies for degradation of microplastics generated from COVID-19 healthcare waste

COVID-19 pandemic has led to the generation of massive plastic wastes, comprising of onetime useable gloves, masks, tissues, and other personal protective equipment (PPE). Recommendations for the employ of single-use disposable masks made up of various polymeric materials like polyethylene, polyurethane, polyacrylonitrile, and polypropylene, polystyrene, can have significant aftermath on environmental, human as well as animal health. Improper disposal and handling of healthcare wastes and lack of proper management practices are creating serious health hazards and an extra challenge for the local authorities designated for management of solid waste. Most of the COVID-19 medical wastes generated are now being treated by incineration which generates microplastic particles (MPs), dioxin, furans, and various toxic metals, such as cadmium and lead. Moreover, natural degradation and mechanical abrasion of these wastes can lead to the generation of MPs which cause a serious health risk to living beings. It is a major threat to aquatic lives and gets into foods subsequently jeopardizing global food safety. Moreover, the presence of plastic is also considered a threat owing to the increased carbon emission and poses a profound danger to the global food chain. Degradation of MPs by axenic and mixed culture microorganisms, such as bacteria, fungi, microalgae etc. can be considered an eco-sustainable technique for the mitigation of the microplastic menace. This review primarily deals with the increase in microplastic pollution due to increased use of PPE along with different disinfection methods using chemicals, steam, microwave, autoclave, and incineration which are presently being employed for the treatment of COVID-19 pandemic-related wastes. The biological treatment of the MPs by diverse groups of fungi and bacteria can be an alternative option for the mitigation of microplastic wastes generated from COVID-19 healthcare waste.

Bioremediation of organic/heavy metal contaminants by mixed cultures of microorganisms: A review

Abstract Although microbial remediation has been widely used in the bioremediation of various contaminants, in practical applications of biological remediation, pure cultures of microorganisms are seriously limited by their adaptability, efficiency, and capacity to handle multiple contaminants. Mixed cultures of microorganisms involve the symbiosis of two or more microorganisms. Such cultures exhibit a collection of the characteristics of each microorganism species or strain, showing enormous potential in the bioremediation of organic or heavy metal pollutants. The present review focuses on the mixed cultures of microorganisms, demonstrating its importance and summarizing the advantages of mixed cultures of microorganisms in bioremediation. Furthermore, the internal and external relations of mixed culture microorganisms were analyzed with respect to their involvement in the removal process to elucidate the underlying mechanisms.

DESCENDING PURULENT MEDIASTINITIS: FEATURES OF THE COURSE, DIAGNOSIS AND TREATMENT

Descending purulent mediastinitis is a rare but a life-threatening disease. The absence of characteristic symptoms and a rare incidence of descending purulent mediastinitis in clinical practice are the main reasons for the late diagnosis of this disease and high mortality due to it. In our practice, we have observed 21 cases of descending purulent mediastinitis. The aim of the study is to characterize the features of the course, methods of diagnosis and treatment for descending purulent mediastinitis used in the setting of a multidisciplinary hospital. The focus of infection was detected in 18 patients (85.7%). In most cases, the etiological factor was odontogenic infection – in the area of the second and third mandibular molars (52.3%). The results of bacterial culture test showed that streptococci (Strepto coccus viridans, β-hemolytic streptococci) and staphylococci (Staphylococcus aureus, hemolytic staphylococci) were most often plated from infected foci. In the subgroup of deceased patients, who made up 47.6% of the total number of patients, mixed cultures of microorganisms containing Staphylococcus aureus were more often detected during bacterial culture tests. These patients had to change groups of antibiotics several times. The unfavorable outcome of descending purulent mediastinitis may be due to a delay in the use of transthoracic mediastinal drainage. Early drainage of the neck and mediastinum, timely thoracotomy should be considered as the treatment method of choice in patients with descending purulent mediastinitis.

Mixed culture microorganisms fermented soybean meal improves productive performance and intestinal health of Nile tilapia ( Oreochromis niloticus ) juveniles fed plant‐based diets in a biofloc system

This study aimed to evaluate the effect of plant-based diets containing different inclusion levels (7%, 14%, 21% and 28%) of mixed culture microorganisms fermented soybean meal (FSBM) on the zootechnical performance and intestinal health of juvenile Nile tilapia (Oreochromis niloticus) reared in a biofloc system. The FSBM diets were compared with a positive control diet with fish meal and a negative control diet with no animal protein. All diets were isoprotein (33% CP) and isoenergetic (4300 kcal GE/kg). The design was completely randomized with four replications and the experiment lasted 54 days. Juveniles (1.635 ± 0.198 g) were distributed in 24 tanks (70 L) at a density of seven animals per tank. Fermentation increased probiotic microorganisms count (lactic acid bacteria 4.75 ± 0.21 log CFU g−1 and yeast 3.30 ± 0.54 log CFU g−1) and improved nutritional characteristics of FSBM. In fish fed the diet containing 7% FSBM, growth performance did not differ from fish fed the fish meal diet. FSBM inclusion improved the food efficiency of plant-based diets. The inclusions above 21% of FSBM increased the intestinal villi height. In the inclusion of 28% of FSBM, the goblet cell was higher compared to that of the other plant-based diets. The inclusion of 7% FSBM allows a total replacement of fish meal without compromising the growth performance of the animals.

Polyaromatic hydrocarbons biodegradation using mix culture of microorganisms from sewage waste sludge: application of artificial neural network modelling.

In this study, we aimed to examine the tolerance of mixed culture of microorganisms isolated from sewage waste sludge to degrade high concentrations of polyaromatic hydrocarbons, naphthalene, and phenanthrene. The performance of the artificial neural network (ANN) model to predict and simulate the experimental biodegradation results was investigated. The mixed culture of microorganisms was isolated from sewage waste sludge and adopted to biodegrade naphthalene and phenanthrene at different concentrations (100-1000mg/L). Sewage waste sludge obtained from wastewater treatment plants. A three-layer feed-forward network with a sigmoid transfer function (logsig) at the hidden layer, a linear transfer function (purelin) at the output layer, and a backpropagation training algorithm was used to set the ANN model. The results of this study show that naphthalene at concentrations of 100, 300, 700, and 1000 mg/L was depleted after incubation with the mixed culture for 6, 8, 14, and 16 days, respectively. For phenanthrene, depletion of 100, 300, 600, and 1000 mg/L was achieved after 8, 11, 16, and 19 days of incubation, respectively. A high correlation coefficient of 99.5% between the predicted and the experimental results were obtained by using the AAN model. The results indicated that the mixed culture of microorganisms from sewage waste sludge could effectively consume naphthalene and phenanthrene as carbon and energy sources. Also, the ANN model could efficiently predict the experimental results for biodegradation treatment.

Biodegradation of Naphthalene Using Glass Beads Roller Bioreactor: Application of Artificial Neural Network Modeling

A roller bioreactor containing inert glass beads was employed to enhance naphthalene biodegradation in an aqueous solution. Mixed culture of microorganisms was isolated from sewage waste sludge and adopted for naphthalene biodegradation. The dissolution rate of naphthalene in the aqueous phase was studied at different conditions in the roller reactor. The results indicate that the best conditions for the biodegradation treatment in the roller bioreactor were 40% and 50% loads with 6 mm and 5 mm sized glass beads, respectively, at a rotation speed of 50 rpm. The biodegradation of 300 mg/L naphthalene in the bioreactor in the absence of glass beads proceeded slowly until depletion after seven days. In the presence of glass beads, the biodegradation rate was faster, depleting after only four days. At a concentration of 500 mg/L naphthalene, complete depletion was attained after nine days in the bioreactor with no glass beads and five days in the presence of glass beads. Both the biodegradation rate \(({r}_{s}\)) and the specific growth rate\(\left(\mu \right)\) increased by utilizing the glass beads bioreactor compared with the bioreactor with no glass beads, thus confirming that the presence of glass beads enhances the mass transfer of naphthalene from the solid to the aqueous phase where it becomes available for utilization. An artificial neural network was used to model naphthalene dissolution and biodegradation. Correlation coefficients of 99.2% and 98.3% were obtained between the experimental and predicted output values for dissolution and biodegradation, respectively, indicating that the ANN model can efficiently predict the experimental data.

African Functional Foods and Beverages: A Review

ABSTRACT Functional foods contain health-promoting ingredients, which make them beneficial to humans and potentially help in disease prevention or treatment. The demand for functional foods is growing not just in the developed regions, but also in the developing regions of the world such as in Africa due to heightened consumer awareness on the role of foods in human health. African functional foods are foods of African origin that possess various characteristics like prebiotic, probiotic, satiety, immune modulation, stress-reduction, improved memory, and cardiovascular benefits. Traditionally fermented functional foods prepared from cereals like maize, millet, or sorghum abound in many African countries. Traditional fermentation, often spontaneous, utilizes a mixed culture of microorganisms mostly belonging to the lactic acid bacteria and yeast groups. The present review corroborated these pieces of information into the famous African functional foods and beverages, their sources, and quality attributes. Furthermore, functional foods were explained in very clear terms while evaluating the relationship between functional foods and African consumer’s health benefits. The study peaked at future work and further considerations on the potential of common functional foods from Africa, which are cheap and readily available to the people.

Biological recovery of phosphorus from waste activated sludge via alkaline fermentation and struvite biomineralization by Brevibacterium antiquum.

Struvite biomineralization is a promising method for phosphorus recovery from wastewater treatment plant streams, and the growth of responsible microorganisms in mixed cultures is one of the most critical points for applying this process in pilot and full-scale. This study aimed to investigate the growth and bio-struvite production of Brevibacterium antiquum in mixed sludge culture. Alkaline fermentation was applied at different pH conditions to enhance the phosphorus content of sludge for an efficient recovery, and pH 8 was determined as the most feasible considering the phosphorus release and sludge characteristics. Growth optimization studies showed that NaCl's presence decreases the growth rate of Brevibacterium antiquum and bio-struvite production. At the same time, pH in the range of 6.8-8.2 did not alter the growth significantly. In addition, studies showed the ability of Brevibacterium antiquum in unsterilized fermented sludge centrate to grow and recover the phosphorus as struvite. Thus, our results indicated the potential of struvite biomineralization in full-scale wastewater treatment plants.

Study of acclimatization and kinetics of pollutant degradation by mixed culture microorganisms in restaurant wastewater

With the development of the restaurant industry, a series of environmental problems emerged, including high concentrations of oily wastewater. As a developing country, Indonesia has a large amount of effluent produced that is not processed but is discharged directly to the available pool. In order to handle restaurant wastewater, physical and chemical approaches can be combined with biological degradation (biodegradation). This biodegradation can be increased by bacterial acclimatization, namely by the addition of microorganisms that have been developed that can efficiently degrade pollutants in a contaminated environment. Stages of research were carried out by propagation of bacteria (Seeding), then the acclimatization process was carried out to adapt bacteria to waste, biodegradation process, and calculate the growth rate curve of microorganisms. It was found that the half-saturation constant of mixed culture microorganisms to treat restaurant waste was 41,336, with a maximum growth rate of 0.124 per day.

Novel polyurethane network/organoclay nanocomposites: Microstructure and physicochemical properties

A series of novel polyurethane network/organoclay nanocomposites (PUN-NCs) with different soft segment contents (30–60 wt%) was prepared by in situ polymerization in solution and characterized. PU network (PUN) was made from poly(dimethylsiloxane)-based macrodiol as the soft segment and 4,4′-methylenediphenyldiisocyanate and hyperbranched polyester of the third pseudo generation as the hard segment. Nanocomposites were obtained by dispersion of organically modified montmorillonite (Cloisite 30B) nanofiller (0.5 wt%). The influence of the soft segment content on the functional properties of PUN-NCs was studied by Fourier transform infrared (FTIR), small-angle and near wide-angle X-ray scattering (SWAXS), thermogravimetric analysis (TGA), dynamic mechanical thermal analyses (DMTA), differential scanning calorimetry (DSC), nanoindentation, atomic force microscopy (AFM), scanning electron microscopy (SEM), and swelling behavior, water absorption and contact angle measurements. The biodegradation process was evaluated using mixed cultures of microorganisms that originated from soil. Mechanically strong PUN-NC materials in the form of films were obtained, pointing to good dispersion and the existence of exfoliated morphology of Cloisite 30B within the PUN matrix, and the nanocomposites with the abovementioned characteristics were obtained as a function of the soft segment content. The decrease of the soft segment content induced a higher degree of phase separated microstructure, increase of Young's modulus, hardness, plasticity, storage modulus, glass transition temperature, surface free energy and swelling ability in tetrahydrofuran, but at the same time, it is responsible for the decrease of crosslinking density and hydrophobicity of PUN-NCs. By choosing adequate soft segment content, the prepared materials can potentially be designed for coating applications, such as top coating materials in environmental conditions.

Modeling and Numerical Solution of the Fate of Multicomponent Substrate in Porous Media

A mathematical model was proposed to appropriately describe the fate of multicomponent substrates in porous media especially soil. The model utilised appropriate biodegradation kinetic expressions that better describe the consumption or degradation rate of the substrate. The Equation, with the second and third type boundary conditions in non-dimensionalised form was solved using the Finite Volume method and simulated in the Matlab environment. An experiment, using a 5 cm (inside diameter) x 60 cm (height) glass column packed with severally autoclaved soil spiked with 2 % substrate (a mixture of hexadecane, heneicosane, 1-methylnaphthalene, 2- methylnaphthalene and 1, 3-dimethylnapthalene) and a consortium of organisms (Providential rettgeri, Streptococcus salivarius, Trichoderma harzianum, Aspergillus flavipes, and Candida famata) was set up to validate the model. The result showed that the model describes the fate of each component within the multicomponent substrate. It also indicates that both Peclet and Thiele numbers affect the biodegradation of the substrate. It was observed that small Peclet number should be allowed for effective biodegradation of the substrate. The model was validated with data obtained for an experiment where a mixture of hydrocarbons was degraded with a mixed culture of microorganisms. The results of the experiment were well described by the model indicating that the model can be used to predict compositions of components of a mixture during biodegradation.

Characteristics of the process of biohydrogen production from simple and complex substrates with different biopolymer composition

The work investigated the characteristics of the dark fermentation (DF) process of a number of simple (starch, sunflower oil, peptone, both separately and mixed) and complex (dog food, pig feed, sewage sludge) substrates using a mixed culture of microorganisms, with a controlled pH (5.5), at 55 °C. Peptone and sunflower oil were characterized by the lowest production of H2, namely 5.0 and 2.3 ml H2/g COD, respectively. The specific hydrogen yield from starch was 1.55 mol H2/mol hexose. The addition of peptone and sunflower oil to starch reduced the specific yield of hydrogen from starch by 23%. A large difference in hydrogen production was observed during DF of complex substrates. The specific hydrogen yield from dog food was 46.5 ml H2/g COD or 143.4 ml H2/g carbohydrates; from pig feed – 32.1 ml H2/g COD or 91.6 ml H2/g carbohydrates; and from sewage sludge – 9.3 ml H2/g COD or 98.0 ml H2/g carbohydrates. Possible relationships between the biopolymer composition of substrates and characteristics of the DF process were analyzed using Spearman's rank correlation coefficients. The concentration of carbohydrates, as well as the ratio of carbohydrates/proteins and carbohydrates/fats, were the main factors influencing the high specific yield of H2, its content in biogas, as well as the ratio of H2/soluble metabolites. The concentration of proteins had a statistically significant positive effect on the accumulation of acetate and succinate, and carbohydrates - on the accumulation of caproate.