Microorganisms associated with natural fermentation ofProsopis africana seeds for the production of okpiye

Okpiye is a food condiment prepared by the fermentation ofProsopis africana seeds. The traditional process for the production and microbiological characteristics of the condiment were investigated. During laboratory fermentation that lasted 96h, the mesquite seeds underwent a natural fermentation that was characterised by the growth of microorganisms to 10⁶–10⁸ cfu/g. Several species of bacteria especiallyB. subtilis, B. licheniformis, B. megaterium, Staphylococcus epidermidis andMicrococcus spp were found to be the most actively involved organisms. However, significant contributions to the microbial ecology were made byEnterobacter cloacae andKlebsiella pneumoniae. Lactobacillus spp were present in low numbers towards the end of the fermentation. The presence ofProteus andPseudomonas spp in traditional fermented samples demonstrate the variability which may exist in the microflora of individual fermented samples. Variations in the important microbial groups show thatBacillus spp were the most prevalent species and occurred until the end of fermentation. Temperature, pH and titratable acidity varied with time and were influenced by the metabolic activities of the microorganisms.     

Microbial growth and modification of corn distillers dried grains with solubles during fermentation

Corn distillers dried grains with solubles (DDGS) were fermented with bacteria or yeast. The microbial growth on three DDGS media-unmodified DDGS, enzyme-pretreated DDGS, and supplemented DDGS - was compared with standard media. Comparative growth profile indicated peaks in microbial growths at different times. The highest specific growth rates (SGR) of 0.6, 0.54 and 0.51 h⁻¹ were observed for Saccharomyces Boulardii on unmodified DDGS, yeast extract, and enzyme-modified DDGS, respectively. Pediococcus Acidilactici and Lactobacillus Plantarum had the SGR of 0.17 and 0.07 h⁻¹, respectively, on control DDGS. However, L. Plantarum on unmodified DDGS demonstrated the highest cell count (2.91 × 10¹¹ CFU/mL), followed by S. boulardii at 1.5 × 10⁹ CFU/mL on YEPD, and P. acidilactici at 1.16 × 10¹⁰ CFU/mL on MRS (de Man, Rogosa and Sharpe) media. Protein digestibility of DDGS improved slightly due to fermentation, and resulted in reduced phytic acid content for some treatments. Production of lactic acid was highest on unmodified DDGS.     

Influence of temperature on the fermentation of bambara groundnut (Vigna subterranea) to produce a dawadawa-type product

Bambara groundnut (Vigna subterranea) was fermented to produce a dawadawa-type product using a starter culture of Bacillus licheniformis isolated from naturally fermenting bambara groundnut beans. Fermentation was carried out at 30 and 37 °C for four days and at 45 °C for two days. The pH of the substrate decreased after 24 hours and then rose at 30 and 37 °C but remained constant at 45 °C after the initial drop. Total titratable acidity of the fermenting beans mimicked the pH values. Proximate analyses for moisture, protein and fat of the cotyledons showed an increase in all three constituent at each of the three fermentation temperatures. At the end of fermentation, total available carbohydrate was 55%, 59% and 62% of the original value at 30, 37 and 45 °C, respectively. Fermentation of bambara groundnut at 45 °C for two days is recommended as the ideal fermentation temperature and time.     

Microbial populations associated with the retting of melon pods ( Colocynthis citrullus L.) during seed recovery

The traditional process for the retting of melon pulp and microbiological characteristics in the recovery of melon seeds ( Colocynthis citrullus L.) were investigated. Melon pods were sliced open and exposed for seven days. The pulp underwent a natural fermentation that was characterised by the growth of microorganisms to 108–1010 cfu/g. The pH fluctuated between 4.8 and 5.1 with a lactic acid content of 0.72%. Bacillus subtilis, B. polymyxa, Lactobacillus fermentum, L. brevis and Streptococcus faecalis were the predominant microorganisms but, significant contributions were made by Staphylococcus saprophyticus and Enterobacter cloacae. Penicillium, Aspergillus and Rhizopus species including the yeasts, Sacharomyces cerevisiae Candida krusei and Deboromyces hansenii were isolated from the fermentation. Growth of microorganisms was completely inhibited in antibiotic-treated samples indicating that the melon pods were the main source of microorganisms for the fermentation.     

Extended shelf-life of liquid fermentation derived talc formulations of Trichoderma harzianum with the addition of glycerol in the production medium

Liquid fermentation based formulations of Trichoderma spp. are vulnerable to desiccation compared to solid state fermentation based formulations. The effect of the addition of glycerol, an osmoticant in the production medium on the shelf-life of Trichoderma harzianum was studied. The addition of glycerol at 3, 6 or 9% reduced the water activity in the medium. Both in shaker culture and fermentor, the addition of glycerol in production medium prolonged the shelf-life of talc formulation. The addition of glycerol at 3 and 6% extended the shelf-life (with viability of >2 × 10⁶ CFU g⁻¹) to 7 and 12 months, respectively compared to 4-5 months shelf-life in formulations derived without the addition of glycerol. Regression analysis showed that there was positive correlation between colony forming unit (CFU) and water activity. In bio-efficacy tests, even after storage for 12 months, formulations derived with the addition of glycerol at 3 or 6% in the production medium could protect the tomato plants from Fusarium wilt incidence by 44-50%. The use of addition of osmoticants in production medium for enhancing the shelf-life of liquid fermentation derived fungal formulations is discussed.     

Research progress of vegetable oil and derivative in microbial fermentation for high-value-added metabolite production

Vegetable oil and derivative,as well as waste cooking oil,are important resources for microbial fermentation to produce high-value-added metabolites.Diversity of their compositions not only provides more choices for the fermentation by different microorganisms,but also is a challenge for their systematic utilization.According to the previous literature,4 main functions of vegetable oil and derivative can be summarized,such as carbon source,precursor,inducer and cell protectant during fermentation process.Currently,there is still insufficient knowledge about application of vegetable oil and derivative for high-value-added metabolite production.Therefore,this article firstly presented a comprehensive summary of compositions of vegetable oils and their derivatives,variety of corresponding microbial metabolites,limiting factors and optimization of fermentation process.     

Modeling the effects of solid state fermentation operating conditions on endoglucanase production using an instrumented bioreactor

Cellulase production is one of the most critical steps in the economics of second generation ethanol. Although solid-state fermentation (SSF) is an attractive process for the production of enzymes, SSF is highly limited by the difficulty in controlling the operating variables which affect microbial growth and metabolites production. In this context, this work evaluates the effects of operational conditions on endoglucanase production by a selected strain of Aspergillus niger cultivated under SSF using an instrumented lab-scale bioreactor equipped with an on-line automated monitoring and control system. The effects of air flow rate, inlet air relative humidity and substrate initial moisture on endoglucanase production were evaluated using a statistical design methodology. A correlation coefficient of 0.9106 and a calculated value of F, 5.46 folds higher than the listed value (P-value < 0.05) allowed the modeling of endoglucanase production under different process conditions. Higher endoglucanase production (56.1 U/g) was achieved for a selected condition of substrate initial moisture of 72%, air inlet humidity of 70%, and flow rate of 20 mL/min. A significant increase in endoglucanase production was also found to be achieved under forced aeration conditions (50.2 IU/g) compared to static conditions (29.8 IU/g) after 72 h of cultivation. Besides, respirometric analysis revealed that the total amount of CO₂ produced was linearly correlated with enzyme production (R² of 0.988). The bioreactor system used, as well as the methodology employed herein, was very effective in evaluating the influence of operational variables on enzymes production under SSF.     

Optimization of ethanol production by Saccharomyces cerevisiae UFPEDA 1238 in simultaneous saccharification and fermentation of delignified sugarcane bagasse

Ethanol production by Saccharomyces cerevisiae UFPEDA1238 was performed in simultaneous saccharification and fermentation of delignified sugarcane bagasse. Temperature (32 °C, 37 °C), agitation (80; 100 rpm), enzymatic load (20 FPU/g cellulose and 10%, v/v β-glucosidase or 10 FPU/g cellulose and 5% β-glucosidase) and composition of culture medium were evaluated. Ethanol concentration, enzymatic convertibility of cellulose and volumetric productivity were higher than 25 g/L, 72% and 0.70 g/L h, respectively, after 30 h, when the culture medium 1 and 20 FPU/g cellulose/10%, v/v β-glucosidase or the culture medium 2 and 10 FPU/g cellulose/5% β-glucosidase were used in SSF at 37 °C and 80 rpm. In the SSF with culture medium 2 (supplemented with ammonium, phosphate, potassium and magnesium), 150 L ethanol/t bagasse was achieved, with minimum enzyme loading (10 FPU/g cellulose and 5%, v/v β-glucosidase) for 8%, w/v of solids, which is often an important requirement to provide cost-efficient second generation ethanol processes.     

In vitro fermentation patterns and methane production as influenced by cultivar and season of harvest of Lolium perenne L.

In some European countries, the majority of annual enteric methane (CH₄) emissions by ruminants occur at pasture – a direct result of the predominance of grazing within ruminant production systems. However, there are only limited data available as to the effect of perennial ryegrass cultivar and season of harvest on CH₄ production. Using the in vitro gas production technique, the effect of perennial ryegrass cultivar on fermentation characteristics and CH₄ production was determined (Experiment 1) and the persistence of these traits throughout the growing season for two cultivars, identified from Experiment 1 as having either a high or low methanogenic potential, was examined (Experiment 2). In Experiment 1, organic matter (OM) digestibility and cumulative total gas production profiles were unaffected by cultivar but, with regard to the kinetics of CH₄ production, the asymptote value (A), cumulative CH₄ yield at 72 h, and the fractional rate (μ) of CH₄ production at both time of 0·5A(T)(μCH₄T) and at 48 h (μCH₄48h) were significantly (P < 0·05) different. The amount of digested OM, as a proportion of cumulative CH₄ production (DigOM/CH₄) at 24 and 72 h after commencement of inoculation, revealed that the amount of substrate required to produce 1 ml of CH₄ also differed significantly between cultivars (P < 0·01). In Experiment 2, regrowth number significantly modified the majority of measured samples (P < 0·01); cultivar effects were limited to the lag phase of the cumulative CH₄ production curve and DigOM/CH₄ at 8 h only (P < 0·05). These results suggest that differences exist between cultivars in how OM is partitioned following microbial fermentation and that these differences demonstrate persistency throughout the growing season. In the course of time it may be possible to exploit these differences through cultivar selection and plant breeding programmes, and thereby reduce enteric CH₄ emissions within pastoral production systems.     

Some biochemical and nutritional changes during the fermentation of fluted pumpkin (Telferia occidentalis)

The pH, soluble nitrogen, soluble solids and titratable acidity increased during a 6 day fermentation of fluted pumpkin seeds. Gas liquid chromatographic analysis of trimethylsilyl (TMS) dirivatives of carbohydrates extracted from the seeds showed that the unfermented seeds contained mostly sucrose with a low content of flatus-oligosaccharides, raffinose and stachyose. There were also high contents of fructose and galactose. Fermentation increased the total monosaccharides with high content of glucose and some unidentified monosaccharides. Fermentation decreased the total oligosaccharide, eliminated raffinose and stachyose and increased the content of maltose. Except for a slight decrease in total saturated and increase in total unsaturated fatty acids, fermentation had no effect on fatty acid composition.     

Comparative study of microorganisms and sensory attributes of condiments from the fermentation of different seeds

Seeds of African locust bean, melon, castor oil bean and soybean were processed and fermented for 3 days to produce local condiments in the laboratory with a method that simulated the traditional production process. Microorganisms associated with their fermentation and the organoleptic properties of the products were compared.Altogether, seven species of bacteria were involved in the fermentation. These included fiveBacillus spp. and one species each ofPseudomonas andStaphylococcus. Their occurrence vary between the seeds on the different days of fermentation. However,Bacillus spp. were present in all the seeds throughout the fermentation period. The sensory evaluation preference rating for the four products was highest for soybean condiment, followed by that made from locust bean. Melon condiment was the least preferred among the four products. Statistical analysis showed that there were significant differences (P0.05) among the four products for each of the four organoleptic properties evaluated by the judges and also for titratable acidity. Glutamic acid level of soybean condiment was highest (0.31%) among the four products with that of melon being the lowest (0.04%). These results could serve as useful indices for the development of starter culture and optimization of production process in commercializing the production of these local condiments.     

In vitro rumen methane output of grasses and grass silages differing in fermentation characteristics using the gas‐production technique (GPT)

The chemical composition of silage consumed by cattle can influence the subsequent rumen microbial fermentation patterns and methane (CH₄) emissions. The objectives of this study were to (i) evaluate the effect of ensilage on the in vitro rumen methane output of perennial ryegrass and (ii) relate the silage fermentation characteristics of grass silages with in vitro rumen methanogenesis. Three pre‐harvest herbage‐conditioning treatments and seven silage‐additive treatments were used in a laboratory‐scale silo experiment to produce a diversity of silage fermentation characteristics. Ensilage reduced (P < 0·01) the in vitro rumen CH₄ output (mL CH₄ g^?1 dry matter (DM) disappeared). This reflected differences in the direction of rumen fermentation (lower acetic (P < 0·05) and higher propionic (P < 0·001) acid proportions in volatile fatty acids) rather than major changes in the extent of in vitro rumen fermentation (i.e. mmol VFA g^?1 DM). The magnitude of the decrease in CH₄ output (mL g^?1 DM incubated) owing to ensilage increased as the extent of silage fermentation, and in particular the lactic acid concentration, increased. In contrast, among silages with relatively similar extents of silage fermentation (i.e. total fermentation products), an increase in the proportion of lactic acid in silage fermentation products led to a more extensive in vitro rumen fermentation and thus to a greater CH₄ output (mL g^?1 DM).     

Changes in the physical and the sensorial properties of wheat bread caused by interruption and slowing of the fermentation of yeast-based leaven

Here we propose an original study on the effect of an interruption and slowing of the fermentation of yeast-based leaven on the physical properties of bread.     

Separating the effects of forage source and field microbiota on silage fermentation quality and aerobic stability

This study attempted to separate the effects of forage source and field microbiota on silage fermentation quality and aerobic stability. Single samples of grass, red clover and maize were used. Field microbiota was obtained by centrifugation of microbial suspensions of the three samples. The intact forages were dried and sterilized by heating at 60°C for 3 h + 103°C for 15 h, inoculated in a 3 (forage) × 3 (inoculum) design and reconstituted to a dry‐matter level of 400 g kg^?1 before ensiling. After ensiling for 71 d, subsamples were subjected to an 8‐d aerobic stability test, which included temperature and pH measurements. Bacterial community analysis was performed on samples before and after ensiling by 16S rRNA gene amplicon sequencing. Forage source had a marked effect on the levels of lactic acid, acetic acid, ammonia‐N and 2,3‐butanediol, but microbiota source only affected the acetic acid concentration. The forage and microbiota as well as their interactions affected silage stability variables. The maize microbiota improved silage stability, whereas silages made from the maize forage had the poorest stability. Bacterial community analysis revealed higher abundance of lactic acid bacteria on the maize forage, with Lactococcus and Leuconostoc being the dominant genera. These preliminary results suggested that fermentation quality is mainly affected by forage source, whereas the aerobic stability is affected by both forage and field microbiota.     

Value-addition of agricultural wastes for augmented cellulase and xylanase production through solid-state tray fermentation employing mixed-culture of fungi

Solid-state fermentation (SSF) was performed to evaluate the potential of agricultural residues for the production of cellulase and hemicellulase using individual and mixed cultures of Aspergillus niger and Trichoderma reseei. The maximum filter paper (FP) cellulase activity of 13.57 IU/gram dry substrate (gds), 22.89 IU/gds and 24.17 IU/gds and β-glucosidase activities of 21.69 IU/gds, 13.58 IU/gds and 24.54 IU/gds were obtained with wheat bran medium at 96 h incubation period with A. niger, T. reseei and mixed-cultures of A. niger and T. reseei, respectively. Mixed-culture SSF using rice straw supplemented with wheat bran in the ratio 3:2 resulted in higher FP cellulase, β-glucosidase, endoglucanase (CMCase) and xylanase activities, compared to the activities obtained using mono-cultures. Similarly, higher FP cellulase, β-glucosidase, CMCase and xylanase activities of 35.8 IU/gds (96 h), 33.71 IU/gds (96 h), 131.34 IU/gds (120 h) and 3106.34 IU/gds (120 h) were achieved in the tray fermentation using rice straw with wheat bran in the ratio of 3:2. Results of present investigation showed that higher cellulase activity and an optimal combination of cellulase and β-glucosidase can be achieved through mixed-culture SSF in trays. The approach of utilizing negative cost agricultural wastes through tray fermentation for cellulase and hemicellulase production is expected to serve the objectives of: (a) management of wastes which would otherwise cause environmental pollution problems; (b) production of hydrolytic enzymes at low cost and; (c) simple technique requiring no sophisticated instruments with practical applications.     

Enhancing three phenolic fractions of oats (Avena sativa L.) and their antioxidant activities by solid-state fermentation with Monascus anka and Bacillus subtilis

This work aims to improve phenolic fractions of oats and their antioxidant activities by solid-state fermentation (SSF) combining Monascus anka with Bacillus subtilis. Results revealed that the fermentation system significantly (p < 0.05) increased the total phenolic content (TPC), which was 23-fold over that in unfermented oats. The hydrolytic enzyme activities of α-amylase, β-glucosidase, and cellulase were significantly (r > 0.75, p < 0.05) correlated to the TPC, indicated an important role in the release of phenolic in oats. The proportion of free phenolic fraction in oats was increased from 39.76% to 61.62%, while that of bound phenolic fraction decreased from 42.17% to 22.78%. Moreover, the phenolic compositions of free, conjugated and bound phenolic fractions varied with fermentation. It implied that the phenolic compounds in different forms could be converted and transformed in the SSF system. Meanwhile, the DPPH· and ABTS^·+ scavenging activities of the free and conjugated phenolic fractions in oats became stronger after fermentation. It indicated that the changes of antioxidant activities of phenolic fractions might be closely related to the structural modification by microbial enzymes in the SSF system. Consequently, this study provides a prospect fermentation process for improving the phenolic release and antioxidant activities in oats.     

In vitro ruminal fermentation parameters and methane production of Marandu palisadegrass (Urochloa brizantha) in a silvopastoral system associated with levels of protein supplementation

The addition of protein supplementation in a silvopastoral system can contribute to improved forage intake and digestibility. Our objective was to evaluate in vitro ruminal parameters, digestibility and gas production of Marandu palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster] in a silvopastoral system and compare this to parameters obtained from diets with protein supplementation. Forage was sampled during the growing season (November to April) in 2016/17 and 2017/18. In vitro incubation treatments consisted of four levels of protein supplement (20% of crude protein; CP) in the diet (0.1, 0.2, 0.3 and 0.4 g/kg of body weight). The neutral detergent fibre, acid detergent fibre and indigestible neutral detergent fibre concentrations were highest in the first year. In the second year, CP concentration was 21% greater than in the first year. There was a linear increase for digestion rate, a quadratic effect for lag time and a linear decrease for average digestion time as supplementation levels were increased. The least lag time and digestion time occurred in the second year. There was no supplementation effect on ruminal pH, acetate and butyrate concentrations. Second-year in vitro dry matter digestibility (IVDMD) was greater than in the first year. Increases in supplementation levels linearly enhanced IVDMD and reduced methane (CH₄) production. The inclusion of a protein supplement contributed to reduced CH₄ and increased volatile fatty acids production; therefore, we recommended the supplement inclusion of >0.28 g/kg of BW for animals grazing in well-managed palisadegrass pastures.     

Microbial community dynamics and their contributions to organic acid production during the early stage of the ensiling of Napier grass (Pennisetum purpureum)

The study aimed to disclose the microbial community dynamics and their contributions to organic acid production during the ensiling of Napier grass. Napier grass was harvested at the vegetative growth phase and ensiled for 30 days. Three silos were opened after 1, 2, 3, 5, 7, 14, and 30 days of ensiling respectively. The intensive fermentation was observed during the initial stage of ensiling, indicated by lower pH (<4.0) on d 2 of ensiling. Lactic acid (LA) was the primary fermentation product, although acetic acid (AA) concentration rapidly increased and LA/AA concentration gradually decreased after 3 days of ensiling. The ethanol concentration was already 11.8 g/kg DM on d 1 of ensiling and then remained stable until the end of ensiling. Lactococcus was the predominant genus during the initial 2 days of ensiling, and then, it was gradually replaced by Lactobacillus. The increase in ammonia nitrogen and butyric acid concentration after 7 days of ensiling was attributed to the growth of Clostridia, which is favored by the high moisture concentration in the Napier grass. The natural ensiling of Napier grass displayed LA-type fermentation and was dominated by the fermentation of Lactobacillus and Lactococcus. Lactobacillus is mainly responsible for the LA production during the ensiling of Napier grass.     

Effects of formic acid and potassium diformate on the fermentation quality,chemical composition and aerobic stability of alfalfa silage

The objective of this study was to evaluate the efficacy of potassium diformate (KDF) as a potential additive for alfalfa silage. Fresh alfalfa was untreated or treated with formic acid (4 g/kg fresh weight, FW) or three concentrations of KDF (4, 5.5 or 7 g/kg FW). After 60 days of ensiling, the addition of formic acid and greater levels of KDF (5.5 and 7 g/kg) effectively reduced silage pH and inhibited the undesirable bacteria, indicated by lower butyric acid, ethanol, ammonia N concentrations and microbial populations (including enterobacteria, yeasts, moulds and clostridia). Additives decreased the dry‐matter loss, and more water‐soluble carbohydrates were preserved in the silages with formic acid or potassium diformate than in the control. Alfalfa silages treated with formic acid at 4 g/kg FW or potassium diformate at 5.5 or 7 g/kg FW were classified as the highest quality silage based on the higher Flieg's point (above 70) and remained stable for more than 9 days during aerobic exposure. Potassium diformate is recommended as an effective additive for alfalfa silages at a level of 5.5 or 7 g/kg FW under the humid and hot conditions of southern China.     

野生兰属植物菌根真菌的分离和表型鉴定

为鉴定野生兰属植物内生菌根真菌种类,以6种代表性兰属植物春剑、春兰、蕙兰、送春、建兰、莲瓣兰为材料,采用常规分离方法,从其内生菌根中分离得到30个菌株。通过菌落特征和光学显微特征观察,将30种内生菌根真菌初步鉴定为镰刀菌属、毛壳菌属、柱孢霉属和瘤菌根菌属4个种类。