Inoculum Conditions Research Articles

Spatiotemporal dynamics of Phytophthora infestans airborne inoculum in Belgium

AbstractFor nearly a century, scientists have strived to model the development of Phytophthora infestans (Pi) to predict late blight infections in potatoes. This has led to the use of decision support systems (DSSs) that rely on forecasting models based on environmental parameters. All these models assume that the primary inoculum is ubiquitous. This study focuses on the spatiotemporal distribution of airborne inoculum of Pi to assess the value of incorporating quantitative data of this variable in improving the prediction of primary infection of potato late blight in fields. The daily spatiotemporal distribution of Pi airborne inoculum was studied from 2019 to 2022 at Ath, Gembloux, Libramont and Louvain-la-Neuve in Belgium by combining Burkard spore traps with a quantitative PCR assays. The quantities of Pi inoculum trapped daily ranged from 0 to 4903 (expressed as sporangia equivalent) depending on the site and the year. The appearance of late blight symptoms in untreated plots located close to spore traps was assessed shortly after the detection of airborne inoculum in all monitored sites. A comparison between airborne inoculum detection and the recommendations provided by three DSSs revealed that fungicide treatments are often recommended at the beginning of the season when airborne inoculum is absent. Two field trials performed in 2021 and 2022 showed that the number of fungicide treatments could be reduced by considering the presence of the inoculum, particularly by delaying the first application. Further knowledge of the relationships between disease pressure, airborne inoculum and meteorological conditions will provide valuable information for improving DSSs and reducing fungicide use.

Determinant factors for optimal anaerobic digestion of agro-industrial sardine residues

ABSTRACT In this study, nutritious and abundant waste generated by sardine canneries was used as the main substrate to assess the effect of fundamental parameters in anaerobic digestion. The temperature range studied, between 37°C and 45°C, allowed for a comparison between the performance of the thermophilic and mesophilic processes. The free water content in the substrate also enabled us to compare fermentation in solid-state fermentation (SSF) with its counterpart, liquid-state fermentation (LSF). The study parameters also included the integration of Aspergillus niger (AN) and molasses. The results revealed significant effects of the AN inoculum and thermophilic conditions in improving biogas production. Optimal biotransformation generated a safe digestate that complies with French standards for use as a biofertilizer. Germination tests demonstrated that it has no inhibitory effect on tomato seeds and has the potential to enhance crop yields better than chemical fertilisers.

Development of a Robust Saccharomyces cerevisiae Strain for Efficient Co-Fermentation of Mixed Sugars and Enhanced Inhibitor Tolerance through Protoplast Fusion.

The economical and efficient commercial production of second-generation bioethanol requires fermentation microorganisms capable of entirely and rapidly utilizing all sugars in lignocellulosic hydrolysates. In this study, we developed a recombinant Saccharomyces cerevisiae strain, BLH510, through protoplast fusion and metabolic engineering to enhance its ability to co-ferment glucose, xylose, cellobiose, and xylooligosaccharides while tolerating various inhibitors commonly found in lignocellulosic hydrolysates. The parental strains, LF1 and BLN26, were selected for their superior glucose/xylose co-fermentation capabilities and inhibitor tolerance, respectively. The fusion strain BLH510 demonstrated efficient utilization of mixed sugars and high ethanol yield under oxygen-limited conditions. Under low inoculum conditions, strain BLH510 could completely consume all four kinds of sugars in the medium within 84 h. The fermentation produced 33.96 g/L ethanol, achieving 84.3% of the theoretical ethanol yield. Despite the challenging presence of mixed inhibitors, BLH510 successfully metabolized all four sugars above after 120 h of fermentation, producing approximately 30 g/L ethanol and reaching 83% of the theoretical yield. Also, strain BLH510 exhibited increased intracellular trehalose content, particularly under conditions with mixed inhibitors, where the intracellular trehalose reached 239.3 mg/g yeast biomass. This elevated trehalose content contributes to the enhanced stress tolerance of BLH510. The study also optimized conditions for protoplast preparation and fusion, balancing high preparation efficiency and satisfactory regeneration efficiency. The results indicate that BLH510 is a promising candidate for industrial second-generation bioethanol production from lignocellulosic biomass, offering improved performance under challenging fermentation conditions. Our work demonstrates the potential of combining protoplast fusion and metabolic engineering to develop superior S. cerevisiae strains for lignocellulosic bioethanol production. This approach can also be extended to develop robust microbial platforms for producing a wide array of lignocellulosic biomass-based biochemicals.

Optimizing conditions of mycelial inoculum immobilized in Ca-alginate beads: a case study in ectomycorrhizal fungus Astraeus odoratus.

Ectomycorrhizal inoculum has emerged as a critical tool for forest restoration, especially under challenging climate change conditions. The inoculation of selective ectomycorrhizal fungi can enhance seedling survival and subsequent growth in the field. This study optimized the liquid media for mycelial growth of Astraeus odoratus strain K1 and the sodium alginate solution composition for enhanced mycelial viability after entrapment. Using Modified Melin-Norkrans as the optimal media for mycelial cultivation and 2% sodium alginate supplemented with Czapek medium, 0.25% activated charcoal, 5% sucrose, and 5% sorbitol in the alginate solution yielded the highest viability of A. odoratus mycelia. Preservation in distilled water and 10% glycerol at 25°C for 60 days proved to be the most effective storage condition for the alginate beads. Both fresh and preserved alginate beads were tested for colonizing on Hopea odorata Roxb. seedlings, showing successful colonization and ectomycorrhizal root formation, with over 49% colonization. This study fills a crucial gap in biotechnology and ectomycorrhizal inoculum, paving the way for more effective and sustainable forest restoration practices.

Evaluation of Solid-State Fermentation Conditions from Pineapple Peel Waste for Release of Bioactive Compounds by Aspergillus niger spp.

Currently, agroindustrial waste can be used to obtain bioactive compounds. The solid-state fermentation is an alternative for the valorization of these waste and to be able to release bioactive compounds that may be of interest to different industrial sectors. The aim of this study was to evaluate solid-state fermentation conditions using pineapple peel waste as the substrate with Aspergillus niger spp., to release bioactive compounds using a Plackett–Burman exploratory design. Temperature, humidity, inoculum, NaNO3, MgSO4, KCl, and KH2PO4 conditions in the fermentation process were evaluated. The antioxidant capacity was determined, and the main compounds of the fermentation extracts were identified. The results revealed that the Aspergillus niger HT3 strain reached a hydrolyzable tannin release of 10.00 mg/g, While Aspergillus niger Aa20 reached a condensed tannin release of 82.59 mg/g. The KH2PO4 affects the release of condensed tannins with A. niger Aa20, and MgSO4 affects the release of hydrolyzable tannins with A. niger HT3. In addition, a positive antioxidant activity was demonstrated for the DPPH, ABTS, and FRAP technique. The main compounds in the fermented pineapple peel were 3-feruloylquinic acid, caffeic acid, lariciresinol, and 3-hydroxyphloretin 2′-O-xylosyl-glucoside, among others. The solid-state fermentation process is a biotechnological alternative for the release of bioactive compounds.

Variation in growth rates between cultures hinders the cultivation of ammonia-oxidizing bacteria.

Ammonia-oxidizing bacteria, key players in the nitrogen cycle, have been the focus of extensive research. Numerous novel species have been isolated and their growth dynamics were studied. Despite these efforts, controlling their growth to obtain diverse physiological findings remains a challenge. These bacteria often fail to grow, even under optimal conditions. This unpredictable growth pattern could be viewed as a survival strategy. Understanding this heterogeneous behavior could enhance our ability to culture these bacteria. In this study, the variation in the growth rate was quantified for the ammonia-oxidizing bacterium Nitrosomonas mobilis Ms1. Our findings revealed significant growth rate variation under low inoculum conditions. Interestingly, higher cell densities resulted in more stable cultures. A comparative analysis of three Nitrosomonas species showed a correlation between growth rate variation and culture failure. The greater the variation in growth rate, the higher the likelihood of culture failure.

Effects of Protection Time on Infection of Rice Panicle Blast.

Panicle blast, caused by Magnaporthe oryzae, is a destructive disease of rice worldwide. Clarifying the susceptibility of rice panicles at different stages is of great significance for effective disease management. Field experiments were conducted in two paddy fields at Wuyuan County in 2016 and 2017 to determine the effects of head covering and its timing on the infection of rice panicle blast. Results revealed that panicle blast was reduced significantly by covering rice heads with sulfuric acid paper bags, regardless of the covering time, ranging from initial heading to 15 days afterward, suggesting that rice panicles could be infected by blast pathogen even 15 days after initial heading. Panicle blast incidence was also found to be significantly influenced by plant dates, with higher panicle blast incidence observed in plots planted on early dates, suggesting adjusting plant dates could help rice panicles escape the infection by blast pathogen. The results from this study also highlighted the importance of cultivars and environmental conditions to panicle blast. In conclusion, besides planting blast-resistant cultivars, it is important to protect rice heads from the initial heading to the early dough stages, and fungicides should be applied according to infection warnings based on host, inoculum, and weather conditions.

Identification of resistance germplasm in sesame against root and stem rot (Macrophomina phaseolina) of Sesame

3700 accessions of sesame germplasm were sown during kharif 2021 with susceptible and resistant checks in augmented plot design in 3 meter length row in sick plot (artificial inoculum) condition. Out of these accessions, only 53 accessions were resistant against root and stem rot of sesame and disease incidence was less than 10%.

Transferred communities of arbuscular mycorrhizal fungal persist in novel climates and soils

Symbiotic mycorrhizal fungi strongly influence plant establishment and growth particularly in harsh environments, whereby sympatric, presumably co-adapted symbionts are considered particularly beneficial. However, the response of transferred sympatric mycorrhizal fungal communities to new environments remains largely ignored. We therefore studied the relative importance of initial inoculum, soil and climatic conditions on the composition, diversity and root colonization ability of arbuscular mycorrhizal fungal (AMF) communities. To do so, we analyzed the AMF communities in an extensive experiment with two ecotypes of Bouteloua gracilis planted in their sites of origin and in four new sites differing in climate and soil properties.After three seasons of growth, the sympatric AMF communities were little changed by the new abiotic conditions. The composition of the AMF communities in plant roots was most strongly determined by the initial inoculum, while the contribution of divergent soil and climatic conditions was an order of magnitude smaller. The levels of root colonization by AMF, in contrast, were significantly influenced by climatic and soil conditions and did not differ among communities of different origins. Their pattern indicates that mycorrhiza formation is facilitated in the plant's sympatric soil and climatic conditions, but also that transferred AMF communities adjust mycorrhiza formation to new abiotic conditions.

Efficacy of Different Fungicide Spraying Techniques on the Infestation with Kabatiella zeae and Formation of Fusarium Mycotoxins in Forage Maize

The application of fungicides in maize by the commonly used overhead spraying technique is more challenging than in small-grain cereals. Especially in later development stages, when the plant has reached a considerable height, lower plant organs (e.g., ears) may be insufficiently protected, since a large part of the applied fungicide is deposited on the upper leaves. In contrast, lower plant organs can be reached by the dropleg spraying technique, which allows sub-canopy applications. This study investigated the efficacy of fungicide applications during flowering in forage maize using the overhead and dropleg spraying techniques as well as a combination for the control of Kabatiella zeae and mycotoxin-producing Fusarium species, which can affect leaves and ears, respectively. The efficacy was evaluated in field trials under natural K. zeae and artificial Fusarium inoculum conditions in Northern Germany by measuring disease severities of K. zeae on maize leaves, dry matter yields, and concentrations of the Fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEN) at harvest. Fusarium inoculations of main ears at full flowering resulted in significantly higher DON and ZEN concentrations compared to natural Fusarium infections, whereas the dry matter yield was not affected. The strongest disease progressions of K. zeae were determined after flowering on the upper leaves and leaves around the main ear. Disease severities were significantly reduced on the upper leaves by the overhead application and the combination of the overhead and dropleg spraying technique, whereby the three spraying techniques were equally able to decrease the infestation on the yield-essential leaves around the main ear. No differences in dry matter yield were found between the application techniques, but they were significantly higher than in the untreated control. The contamination with DON and ZEN was most effectively reduced by sub-canopy applications using the dropleg technique, whether as a solo application or in combination with the overhead technique. The main ears were reached better with the applied fungicide, reducing Fusarium infections, and therefore, contamination with mycotoxins. The dropleg technique offers an opportunity for improved protection of lower plant organs, especially in tall growing crops. In combination with the overhead spraying technique, the protection of various plant organs along the entire plant with the applied fungicide could be advantageous, especially when different parts of the plant are affected by different fungal diseases.

Biohydrogen production from kitchen organic waste via effective pre-treatment process of dark fermentation

This research aims to highlight the effective pre-treatment process for biohydrogen production from kitchen organic waste in dark fermentation. The complexity of the fermentation process through the competing of the metabolic living bacteria requires a dynamical control of the process through the pre-treatment of the substrate’s mixtures. In this research the pre-treatment process parameters and inoculum condition that affect biohydrogen production via dark fermentation process were investigated. The parameter that affects biohydrogen production via the dark fermentation process have also been analysed. The performance of two inoculums from food waste and cow manure were tested with three different pre-treatment processes: thermal, acid and alkaline. Based on the results, the cow manure inoculum was the best-performing inoculum, producing more H2 compared to food waste inoculum. Furthermore, the substrate and inoculum with thermal shock pre-treatment approaches has increased the biohydrogen generation compared to acid and alkaline pre-treatment.

Biofiltration based on bioactive coatings for the abatement of indoor air VOCs

Biotechnologies are a feasible alternative for indoor air pollutant abatement. Among biotechnologies, bioactive coatings consist of microorganisms embedded in polymeric matrices, allowing a direct contact between microorganisms and gas pollutants, thus enhancing their abatement. Three bioreactors (BR1, BR2 and BR3) were inoculated with a VOC-degrading enriched culture, a latex bioactive coating with the VOC-degrading enriched culture, and a latex bioactive coating with fresh activated sludge. The influence of empty bed residence time (EBRT) and inlet concentrations on the removal of toluene, α-pinene and n-hexane was assessed. BR1 and BR2 achieved steady-state toluene and pinene removals >90% down to 30 s. BR3 lower removals could be attributed to the lack of acclimation of activated sludge. When inlet concentrations were progressively reduced to <2 mg m−3 at 15 s of EBRT, toluene removals increased to >80% in BR1 and BR2, but only to 64.2% in BR3. Pinene removals reached 90.9% in BR1, and >70% in BR2 and BR3. The bacterial population was dominated by Rhodococcus, Mycobacterium, Devosia and Rhodobacteraceae members in BR1 and BR2. No significant and robust hexane removal was observed regardless of the inoculum or operational conditions, probably due to mass transfer limitations, which entailed a low dominance of organisms with this metabolic capability.

Hythane and methane production in a multistage anaerobic hythane reactor (MAHR): Stage separation, functional microbe selection, thermodynamics, and kinetics

The establishment of a multistage anaerobic hythane reactor (MAHR) that integrates biohythane and biomethane production into a single reactor demonstrates promising potential for simultaneously producing hythane and methane. However, separating hythane and methane production in a single reactor remains a challenge, and stages separation in MAHR system is not well understood. Moreover, the necessity to heating pretreatment of the inoculum for acidogenesis and hythane production is impractical for the full-scale application of MAHR due to the extra economic and energy input. Therefore, heating preselected and not preselected inocula were adopted in this study to reveal the biofuel production performance and the mechanisms of stage separation in MAHRs with different inoculum strategies. Results indicated that stable hythane and methane production of MAHR without inoculum preselection could be achieved and maintained after a longer start-up period compared to the preselected inoculum condition. A comparable hythane and methane production and organics conversion performance were observed in the two MAHRs during stable period, in which hythane with a suitable hydrogen concentration (5%-25%) and methane with a high concentration (57%-75%) were produced. Supported by the more stable microbial correlation networks, MAHR without inoculum preselection suggested a higher methane production rate (13.5 ± 2.8 L/L/d) and was resistant to organic loading shock (80 g COD/L/d). Furthermore, microbial diversity, thermodynamics, and kinetic analysis revealed that the stage separation was highly dependent on microbial dynamics, metabolism characteristics, and reactor configurations. Acetogens (Desulfovibrio and Syntrophobacter) and aceticlastic methanogens (Methanosaeta and Methanosarcina) were more likely to wash out form the hythane production zone (Mh) and be enriched in the methane production zone (Mm) compared to acidogens (Streptococcus, Rikenellaceae_RC9_gut_group, Bacteroides, etc.) and hydrogenotrophic methanogens (Methanobacterium and Methanobrevibacter). The results from this study deepened the understanding of functional microbial community dynamics and stage separation mechanisms, which provided insights into the design, start-up, and full-scale operation of MAHR.

A pilot-scale study of the integrated phycoremediation-photolytic ozonation based municipal solid waste leachate treatment process

Municipal solid waste (MSW) leachate is a highly polluted liquid that accumulates in the landfill and contains a high concentration of toxic pollutants which can pollute the surrounding surface water and groundwater as well, if not treated properly. In this study, an integrated approach of phycoremediation with photolytic ozonation was employed for the leachate collected from the MSW dumpsite which has high Chemical Oxygen Demand (COD) and ammonium (NH4+) levels. Photolytic ozonation treatment was employed as a pre-treatment step under operating parameters of pH: 9.0; Ozone dosage: 5 g/h; UV-C: λ = 254 nm; and contact time: 60 min, in which the COD and NH4+ in the leachate was reduced up to 81% and 95%, respectively. The selected algae Chlorella vulgaris (C.vulgaris) was employed in a lab-scale study to optimize the inoculum conditions in the photolytic ozonated leachate (POL). The specific growth rate of C.vulgaris was observed as 0.14/d in the POL at the optimized condition (inoculum size of 25% (T25)) during the study period of 11 days. High-rate algal pond (HRAP) was employed for the pilot-scale study in controlled environmental conditions as in the T25 experimental run for the assessment of POL treatment and biomass production. C.vulgaris reduced the concentration of pollutants COD, NH4+, and heavy metals (Cu, Fe) in the POL up to 93%, 94%, and 71%, respectively, with the dry biomass productivity of 0.727 g/L/d which is 3 times higher than the biomass productivity of C.vulgaris in freshwater conditions. The biochemical composition (carbohydrates, proteins, and lipids) of the harvested biomass has higher lipid production with lipid productivity of 120 mg/L/d which can be used as a feedstock for the production of value-a dded products.

Comparative study between compost and granular sludge inoculums as promising microbial consortia sources for biohydrogen production from food industry wastewater

This study performed a comparative analysis of anaerobic microbial communities from compost or granular sludge inoculum over the course of industrial substrate codigestion in order to identify the range of carbon-nitrogen ratios (20 to 50) that increase the biohydrogen production. The batch bioreactors were operated at pH = 5.5 ± 0.3 and 35 °C. Physicochemical characterization showed a pH < 4.0 after 32 h; a gradual decrease in organic matter was observed, reaching a maximum of 90% recovery. The highest biohydrogen yield was 72.9 ± 5.7 mL H2 g−1CODrem, which occurred after conducting fermentation with compost inoculum at a carbon–nitrogen ratio of 35. These fermentation processes were characterized by the proliferation of native populations from the substrate (Lactobacillus and Lactococcus) and the intrinsic inoculum conditions (Citrobacter spp. and Megasphaera elsdenii). A shift in the dominant biohydrogen-producing microbial population over time was observed mainly for reaction systems with high biohydrogen yields. Citrobacter spp., Kluyvera cryocrescens, and Rahnella spp. all proliferated during the codigestion processes facilitated by the compost inoculum samples, while Megasphaera elsdenii performed a similar function in the granular sludge inoculum bioreactors.

Genome Sequence Resource for Strains of Pseudomonas syringae Phylogroup 2b and P. viridiflava Phylogroup 7a Causing Bacterial Stem Blight of Alfalfa.

Genome Sequence Resource for Strains of Pseudomonas syringae Phylogroup 2b and P. viridiflava Phylogroup 7a Causing Bacterial Stem Blight of Alfalfa.

Ontogenic Susceptibility of Grapevine Clusters to Ripe Rot, Caused by the Colletotrichum acutatum and C. gloeosporioides Species Complexes.

Natural infection by Colletotrichum spp. and the subsequent development of ripe rot were observed in susceptible grape (Vitis vinifera) clusters either protected or exposed to environmental conditions and naturally occurring inoculum by the application or removal of paper bags at various phenological stages at two Mid-Atlantic vineyards. During each of the three experimental seasons, most treatments with grape clusters that were exposed between veraison and harvest developed significantly more severe ripe rot than clusters that were exposed during only the early season or protected throughout the entire season. Spore traps were placed in one vineyard over two seasons and were analyzed via quantitative PCR. DNA of the Colletotrichum acutatum and C. gloeosporioides species complexes was detected from the bloom to the harvest stage, with a higher quantity of C. acutatum DNA than C. gloeosporioides DNA. From ripe rot symptomatic clusters, 417 isolates were collected, and a multilocus phylogenetic analysis of 51 representative isolates identified six Colletotrichum spp., with C. fioriniae (C. acutatum complex) being the most frequently isolated. Weather data were also monitored, and ripe rot-conducive conditions were observed at multiple times throughout each season. In summary, only clusters that were exposed to inoculum and environmental conditions in the late season developed severe ripe rot. The data collected in this study suggest that grape clusters have ontogenic susceptibility to ripe rot, becoming more susceptible as they mature, in contrast to the susceptible bloom stage for other fruit rotting diseases of grapevine.

Complete Genome Sequence Resource for Xanthomonas translucens pv. undulosa MAI5034, a Wheat Pathogen from Uruguay.

Complete Genome Sequence Resource for Xanthomonas translucens pv. undulosa MAI5034, a Wheat Pathogen from Uruguay.

AscotraceR: An R Package Resource to Simulate the Spatiotemporal Spread of Ascochyta Blight in a Chickpea Field Over a Growing Season.

ascotraceR: An R Package Resource to Simulate the Spatiotemporal Spread of Ascochyta Blight in a Chickpea Field Over a Growing Season.

Inoculation conditions improved the pectinase productivity in Aspergillus niger LB-02-SF solid-state cultivation

In this work, the pectinase production by Aspergillus niger LB-02-SF was evaluated in relation to the inoculation conditions of solid-state cultivations carried out in Becher flasks and in rotating drum bioreactor. From the inoculation by spore suspension in the concentration of 7 × 107 spore/100 g of wet medium (gwm), which is standard inoculum condition, were evaluated: different concentrations of spore suspension (from 7 × 104 to 7 × 108 spore/100 gwm), solid vegetative inoculum using 50 and 100 gwm of fermented solid medium (obtained from 48 h of A. niger cultivation in Becher flasks, in a humidified atmosphere, 30 °C) and liquid vegetative inoculum in the proportions of 5 and 10% (v/w) (obtained from 18 h of A. niger cultivation at 300 rpm, 28 °C). In comparison to the standard condition, with the use of the lowest spore concentration (7 × 104 spore/100 gwm), 100 gwm of solid vegetative inoculum and 10% (v/w) of liquid vegetative inoculum, higher pectinases productivities were observed, around 48, 42 and 85%, respectively. The results obtained indicate that the three inoculation strategies defined are alternatives to increase the enzyme productivity and to facilitate the inoculum preparation stage aimed at applying this process on an industrial scale.