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Biofilm Formation and Genetic Diversity of Microbial Communities in Anaerobic Batch Reactor with Polylactide (PLA) Addition
In this paper, an anaerobic digestion (AD) study was conducted on confectionery waste with granular polylactide (PLA) as a cell carrier. Digested sewage sludge (SS) served as the inoculum and buffering agent of systems. This article shows the results of the analyses of the key experimental properties of PLA, i.e., morphological characteristics of the microstructure, chemical composition and thermal stability of the biopolymer. The evaluation of quantitative and qualitative changes in the genetic diversity of bacterial communities, performed using the state-of-the-art next generation sequencing (NGS) technique, revealed that the material significantly enhanced bacterial proliferation; however, it does not change microbiome biodiversity, as also confirmed via statistical analysis. More intense microbial proliferation (compared to the control sample, without PLA and not digested, CW–control, CW–confectionery waste) may be indicative of the dual role of the biopolymer—support and medium. Actinobacteria (34.87%) were the most abundant cluster in the CW–control, while the most dominant cluster in digested samples was firmicutes: in the sample without the addition of the carrier (CW–dig.) it was 68.27%, and in the sample with the addition of the carrier (CW + PLA) it was only 26.45%, comparable to the control sample (CW–control)—19.45%. Interestingly, the number of proteobacteria decreased in the CW–dig. sample (17.47%), but increased in the CW + PLA sample (39.82%) compared to the CW–control sample (32.70%). The analysis of biofilm formation dynamics using the BioFlux microfluidic system shows a significantly faster growth of the biofilm surface area for the CW + PLA sample. This information was complemented by observations of the morphological characteristics of the microorganisms using fluorescence microscopy. The images of the CW + PLA sample showed carrier sections covered with microbial consortia.
Spatial and Temporal Variability of the Microbiological and Chemical Properties of Soils under Wheat and Oilseed Rape Cultivation
The size of the microbial biomass and the activity of soil enzymes are among the most sensitive indicators of agricultural land quality. The aim of this study was to determine the spatial and temporal variability of microbial biomass, the activity of dehydrogenase (DHA) enzyme and the concentration of micro- (Na, Mg and Ca) and macroelements (Cu, Zn, Mn and Fe) in the soil, collected from 37 measurement sites (depth 0–30 cm) in a 40-hectare field during two growing seasons (wheat and oilseed rape). The percentage of nitrogen (%N) in the wheat grain and rapeseeds was also determined. Mapping the spatial distribution of the microbial biomass, the level of DHA activity and the concentration of the selected elements was used to assess the soil productivity. All tested soil parameters exhibited temporal and spatial variability. The creation of raster maps showing the distribution of the tested parameters allowed the observation of a higher nitrogen content in wheat grains in the south-western part of the field, with high values of DHA activity, bacterial biomass and soil pH. In the case of oilseed rape, plants grown in the northern part of the field were characterized by a higher nitrogen content in the grain, where the soil was characterized by a higher content of fungal biomass. On the basis of the obtained research results, a positive, statistically significant correlation was also shown between the biomass of bacteria and the level of DHA in the soil under the cultivation of both wheat and rape. The cultivation of both crops had a significant impact on the size of the microbial biomass pool and on the DHA activity level but did not affect the concentration of the nutrients in the soil. High concentrations of the analyzed elements at the measuring points correlated with a greater %N content in the grain/seeds of the crops harvested at those locations in the field. The results conclude that the mapping of the physicochemical parameters, microbial biomass and activity on the field permits the development of an effective strategy for maintaining sustainable soil productivity through the appropriate management of agricultural practices and the better approximation of mineral fertilization.
Nośniki w fermentacji metanowej bioodpadów: ujęcie procesowo–mikrobiologiczne na przykładzie wybranych układów
Combination of cover crops and bacterial consortia reduce weediness in organic spelt wheat in Central Europe
Cultivation technologies based on the use of microbiological preparations or the introduction of cover crops in organic farming are alternatives to chemical plant protection products. To confirm this hypothesis, field studies were conducted in central Poland in 2019–2022 to determine the effect of bacterial consortia and green fertilizers from cover crops on the dry mass, abundance and species composition of dominant weed species occurring in spelt wheat grown in organic farming. Two factors were researched: I. Bacterial consortia: control treatment (no bacteria), bacterial consortium I (Azotobacter chroococcum + Azospirillum lipoferum Br17), bacterial consortium II (Bacillus megaterium var. phosphaticum + Arthrobacter agilis), bacterial consortium III (Azotobacter chroococcum + Azospirillum lipoferum Br17 + Bacillus megaterium var. phosphaticum + Arthrobacter agilis), II. Cover crops: control treatment (no cover crops), red clover, red clover + Italian ryegrass, and Italian ryegrass. Spelt wheat was harvested in late July. Just before harvesting, weeds were sampled to determine their dry matter, number, and species composition. The research clearly demonstrated that the application of bacterial consortia with cover crops significantly reduced the dry matter and number of weeds, including the dominant species. The greatest reduction in weed number was recorded in treatments after the application of bacterial consortium III in combination with plowing cover crops of red clover and a mixture of red clover and Italian ryegrass.
Efektywna stabilizacja pofermentu z biogazowni rolniczej z wykorzystaniem biowęgla i mikroorganizmów promujących wzrost roślin
Sustainable Methods of Soybean Cultivation in Poland
Many countries in Europe are struggling with a shortage of feed protein; moreover, efforts are being made to limit the import of post-extraction soybean meal, most often from GMO crops. To achieve the above assumptions, varietal progress is necessary and, above all, breeding work should aim at greater adaptation to regional conditions. This study was designed to evaluate the potential for growing Ukrainian soybean ‘Annushka’ in the southeastern Baltic Sea area, in accordance with the application of mineral nitrogen fertilizer and the inoculation of seeds with Bradyrhizobium japonicum. Soybean ‘Annushka’ yielded 0.98–1.68 t ha−1 in the conditions of central Poland. Our experiments have shown significant variations in seed, protein, and fat yields over the years. The maximum amounts of these characteristics were recorded in 2017. Nitrogen fertilization combined with seed inoculation with B. japonicum has proven to be an important factor in improving soybean yields; however, it slightly modified the content of organic compounds in seeds. Improvement in seed and protein yields relative to the control amounted, respectively, to Nitragina + 30 kg N ha−1 (58.8%; 72.6%), HiStick® Soy + 30 kg N ha−1 (57.6%; 68.3%), and Nitroflora + 60 kg N ha−1 (57.6%; 71.9%).
Influence of plant growth-promoting bacteria and green manures on the degreeof weed infestation in Triticum spelta in organic farming
Diversity of Bacterial Communities in Horse Bean Plantations Soils with Various Cultivation Technologies
Modern agriculture should limit its degrading impact on the soils, the natural environment, and the climate. No-tillage soil cultivation technologies, which have been in use for many years and are constantly being improved, are a good example of these actions; although, in-depth studies on their impact on the soil microbial community are currently scarce. The aim of our study was to evaluate the effect of cultivation technology on the soil bacterial community to assess differences that can be reflected in the environmental and agricultural functionality, identifying possible bacterial species with ecological properties. In this context, the composition of bacterial communities (at the phyla, order, class, and species levels) was evaluated under different conditions, such as conventional tillage (CT) (plophing), reduced tillage (RT) (stubble cultivator), strip tillage (ST), and no-tillage (direct sowing on stubble and fallow buffer zone of the experimental field), in a horse bean plantation. Metagenomic methods (next generation sequencing technology, NGS) were used to determine the percentage of individual operational taxonomic units (OTUs). Our study showed that no-tillage cultivation technologies, mainly strip and no-tillage methods, had a positive effect on microbiological communities. In fact, key species related to soil fertility and crop yield, such as Gemmatimonas aurantiaca (a microorganism that reduce nitrous oxide, N2O in soil) and Aeromicrobium ponti (a beneficial species for the soil environment, essential for the proper functioning of the crop agroecosystem), increased in reduced cultivation technologies. These species can determine soil fertility and crop yields, and therefore, they are very important for sustainable and even regenerative agriculture. Further studies of soil samples collected from other crop plantations under different cropping systems may indicate beneficial microbial species that are important for soil fertility.
Anaerobic Digestion of Food Waste—A Short Review
In recent years, growing environmental awareness, the need to reduce greenhouse gas emissions, and the energy crisis have led many countries to seek alternative energy sources. One of the most promising solutions is biogas production via anaerobic digestion (AD), whose substrate can be organic-rich and easily biodegradable food waste (FW). This waste is a significant part of the global waste problem, and its use for energy production is beneficial to both the environment and the economy. This paper presents important issues concerning the monitoring of the AD process, as well as standard and innovative, for the implementation of this process, technological solutions. The aim of the measures taken to optimise the process is to increase AD efficiency and obtain the highest possible methane content in biogas. Two approaches—pretreatment and anaerobic co-digestion (AcoD)—have been integral to the implementation of AD of food waste for years. They are presented in this paper based on a review of recent research developments. Pretreatment methods are discussed with particular emphasis on mechanical, chemical and biological methods. The AcoD of FW with different organic substrates has been extensively reviewed, as confirmed by numerous studies, where higher buffer capacity and optimum nutrient balance enhance the biogas/methane yields. Attention was also paid to the parameters, operating mode and configurations of anaerobic digesters, with a thorough analysis of the advantages and disadvantages of each solution. The article concludes with a brief presentation of the development perspectives for the discussed FW management method and recommendations.
Czy mikrobiologiczne bioherbicydy mogą być alternatywą dla chemicznych środków ochrony stosowanych w uprawie buraka cukrowego?
A Case Study on the Effect of Foliar Nitrogen Fertilization on the Microbiological and Biochemical State of the Soil and the Uptake of Macro- and Microelements by Winter Triticale (Triticosecale)
Due to the increasing demand for food, the agricultural sector is facing a huge challenge related to its production without having a negative impact on the environment. The above issues are regulated by the current EU policy, indicating the need to conduct plant production by the European Green Deal strategy (2020), based on reducing the use of chemical plant-protection products by 50% and reducing the level of mineral fertilization by 20% by 2030. Using appropriate techniques of applying mineral fertilizers, which have a positive effect on the development and activity of soil microorganisms, the availability of nutrients in the soil can be increased while reducing fertilizer applications. This study aims to show whether the use of foliar nitrogen fertilizers in combination with sulfur in a two-year field experiment with triticale stimulates the multiplication of selected groups of microorganisms and the level of soil enzymatic activity. In addition, effects on the content of available forms of nutrients in the soil, triticale yield, and total nutrient uptake were analyzed. It is shown that the applied foliar fertilizers enriched with sulfur, compared to fertilization with ammonium nitrate, contributed to a 100% increase in the number of analyzed groups of microorganisms, urease, and alkaline phosphatase activity; a 44% increase in dehydrogenase activity; and a 15% increase in acid phosphatase activity. The hybrid application technique, with reduced doses of nitrogen fertilizers enriched with sulfur by 20 and 25%, resulted in grain yields exceeding 8 t/ha. Moreover, compared to conventional fertilization based on ammonium nitrate, an increase in the grain yield of triticale was obtained in the range of 16 to 24%, as well as an increase in the accumulation of nutrients in the plant. It is shown that foliar fertilization is a promising alternative to standard fertilization techniques.
Effects of growing spring barley in organic agriculture as a result of constructed bacterial consortia and living mulch
Innovative Spring Barley Cultivation Technology Based on the Use of Microbial Products Together with Living Mulch in Organic Farming
Field research was conducted in Poland in 2019–2021 to determine the effect of microbial products and living mulches on grain yield and grain yield structure elements as well as the biological index of soil fertility (BIF) in spring barley grown in organic agriculture. Two factors were examined: I. microbial products: control (no treatment with microbial products), inoculation with phosphorus-releasing bacteria (Bacillus megaterium var. phosphaticum, Arthrobacter agilis), and co-inoculation (simultaneous inoculation) with phosphorus-releasing bacteria (Bacillus megaterium var. phosphaticum, Arthrobacter agilis) and nitrogen-fixing bacteria (Azospirillum lipoferum Br17, Azotobacter chroococcum); II. living mulch: control (no living mulch—spring barley grown in a pure stand), red clover, red clover and Italian ryegrass, and Italian ryegrass. The study results demonstrated that the highest grain yield at 4.5 t ha−1 with superior structure was produced by spring barley following co-inoculation with phosphorus-releasing bacteria (Bacillus megaterium var. phosphaticum, Arthrobacter agilis) and nitrogen-fixing bacteria (Azospirillum lipoferum Br17, Azotobacter chroococcum). The highest value of the biological index of soil fertility (BIF II) determined at the flowering stage was obtained in plots with spring barley cultivated with the living mulch of red clover mixed with Italian ryegrass or red clover following inoculation with phosphorus-releasing bacteria and nitrogen-fixing bacteria 6.9 and 5.7, respectively.
The Use of Fungi of the Trichoderma Genus in Anaerobic Digestion: A Review
Plant waste biomass is the most abundant renewable energy resource on Earth. The main problem with utilising this biomass in anaerobic digestion is the long and costly stage of degrading its complex structure into simple compounds. One of the promising solutions to this problem is the application of fungi of the Trichoderma genus, which show a high capacity to produce hydrolytic enzymes capable of degrading lignocellulosic biomass before anaerobic digestion. This article discusses the structure of plant waste biomass and the problems resulting from its structure in the digestion process. It presents the methods of pre-treatment of lignocellulose with a particular focus on biological solutions. Based on the latest research findings, key parameters related to the application of Trichoderma sp. as a pre-treatment method are discussed. In addition, the possibility of using the digestate from agricultural biogas plants as a carrier for the multiplication of the Trichoderma sp. fungi, which are widely used in many industries, is discussed.
Polylactide (PLA) as a Cell Carrier in Mesophilic Anaerobic Digestion—A New Strategy in the Management of PLA
The management of waste polylactide (PLA) in various solutions of thermophilic anaerobic digestion (AD) is problematic and often uneconomical. This paper proposes a different approach to the use of PLA in mesophilic AD, used more commonly on the industrial scale, which consists of assigning the function of a microbial carrier to the biopolymer. The study involved the testing of waste wafers and waste wafers and cheese in a co-substrate system, combined with digested sewage sludge. The experiment was conducted on a laboratory scale, in a batch bioreactor mode. They were used as test samples and as samples with the addition of a carrier: WF—control and WFC—control; WF + PLA and WFC + PLA. The main objective of the study was to verify the impact of PLA in the granular (PLAG) and powder (PLAP) forms on the stability and efficiency of the process. The results of the analysis of physicochemical properties of the carriers, including the critical thermal analysis by differential scanning calorimetry (DSC), as well as the amount of cellular biomass of Bacillus amyloliquefaciens obtained in a culture with the addition of the tested PLAG and PLAP, confirmed that PLA can be an effective cell carrier in mesophilic AD. The addition of PLAG produced better results for bacterial proliferation than the addition of powdered PLA. The highest level of dehydrogenase activity was maintained in the WFC + PLAG system. An increase in the volume of the methane produced for the samples digested with the PLA granules carrier was registered in the study. It went up by c.a. 26% for WF, from 356.11 m3 Mg−1 VS (WF—control) to 448.84 m3 Mg−1 VS (WF + PLAG), and for WFC, from 413.46 m3 Mg−1 VS, (WFC—control) to 519.98 m3 Mg−1 VS (WFC + PLAG).
Response of Soil Microorganisms to and Yield of Spelt Wheat following the Application of Bacterial Consortia and the Subsequent Effect of Cover Crops in Organic Farming
In modern agriculture, more and more attention is being paid to the use of microorganisms that can increase crop productivity and quality even under adverse weather conditions. Due to the declining biodiversity of crops and the occurrence of soil erosion and nutrient losses, the introduction of cover crops (CC) can be a positive crop management technique. In the field study presented here, the effect of growing spring barley with CCs applied simultaneously with bacterial consortia on the ratio of the total number of bacteria to actinobacteria (B/A) and the number of fungi in the soil was evaluated. The biomass yield of CCs and the subsequent effect on the yield of spelt wheat grown with the application of bacterial consortia were also evaluated. The bacterial consortia applied included consortium 1, comprising Bacillus subtilis, Bacillus amyloliquefaciens, and Pseudomonas fluorescens, and consortium 2, comprising Bacillus subtilis, Bacillus amyloliquefaciens, Pseudomonas fluorescens, and Azotobacter chroococcum. The CCs were red clover, red clover + Italian ryegrass, and Italian ryegrass. The most favorable B/A ratio and the highest number of fungi were obtained after growing spring barley with a CC consisting of a mixture of red clover and Italian ryegrass when using bacterial consortium 2. These conditions additionally had the most favorable influence on spelt wheat. The combination of such a forecrop with the application of bacterial consortium 2 resulted in the highest yields of spelt wheat.
