A comparative study of the effects of microbial agents and anaerobic sludge on microalgal biotransformation into organic fertilizer

Polystyrene nanoplastics shape microbiome and functional metabolism in anaerobic digestion

Nanoplastics (NPs) and microplastics (MPs) are ubiquitous in the natural environment, social production, and life. However, our understanding of the effects of NPs and MPs on shaping the microbiome and functional metabolism of anaerobic microorganisms is limited. We investigated the response of core microbiomes and functional genes to polystyrene (PS) NPs and MPs exposure in a representative anaerobic micro-ecosystem of waste activated sludge. Independent anaerobic digestion (AD) experiment indicated that PS nanobeads suppressed acidogenesis by inhibiting the activity of acetate kinase, and subsequently reduced methane production. Our findings confirmed that MPs (1 and 10 μm) had no perceptible effect on methane production, yet 50 nm NPs resulted in a 15.5% decrease in methane yield, perhaps driven by the behavior of dominant genera Sulfurovum, Candidatus Methanofastidiosum, and Methanobacterium. Assays revealed that NPs contributed to the simplest network assemblies in bacterial communities, contrary to empirical networks in archaeal communities. NPs significantly reduced the abundance of genes involved in carbon degradation: lig, naglu and xylA, as well as gcd and phnK related to phosphorus cycling. The absolute abundance of mcrA encoding methyl-coenzyme M reductase was 54.4% of the control assay. PS NPs might adversely affect the biodiversity and biogeochemical cycles in natural and artificial ecosystems through their negative impact on biomass energy conversion by anaerobic microorganisms.

Progress in microbial biomass conversion into green energy

The increase in global population size over the past 100 decades has doubled the requirements for energy resources. To mitigate the limited fossil fuel available, new clean energy sources being environmental sustainable for replacement of traditional energy sources are explored to supplement the current scarcity. Biomass containing lignin and cellulose is the main raw material to replace fossil energy given its abundance and lower emission of greenhouse gases and NOx when transformed into energy. Bacteria, fungi and algae decompose lignocellulose leading to generation of hydrogen, methane, bioethanol and biodiesel being the clean energy used for heating, power generation and the automobile industry. Microbial Fuel Cell (MFC) uses microorganisms to decompose biomass in wastewater to generate electricity and remove heavy metals in wastewater. Biomass contains cellulose, hemicellulose, lignin and other biomacromolecules which need hydrolyzation for conversion into small molecules by corresponding enzymes in order to be utilized by microorganisms. This paper discusses microbial decomposition of biomass into clean energy and the five major ways of clean energy production, and its economic benefits for future renewable energy security.

Evaluation of Biocompatibility and Antagonistic Properties of Microorganisms Isolated from Natural Sources for Obtaining Biofertilizers Using Microalgae Hydrolysate

Determination of the biocompatibility of microorganisms isolated from natural sources (Kemerovo Oblast—Kuzbass) resulted in the creation of three microbial consortia based on the isolated strains: consortium I (Bacillus pumilus, Pediococcus damnosus, and Pediococcus pentosaceus), consortium II (Acetobacter aceti, Pseudomonas chlororaphis, and Streptomyces parvus), and consortium III (Amycolatopsis sacchari, Bacillus stearothermophilus; Streptomyces thermocarboxydus; and Streptomyces thermospinisporus). The nutrient media composition for the cultivation of each of the three studied microbial consortia, providing the maximum increase in biomass, was selected: consortium I, nutrient medium 11; consortium II, nutrient medium 13; for consortium III, nutrient medium 16. Consortia I and II microorganisms were cultured at 5–25 °C, and consortium III at 50–70 °C. Six types of psychrophilic microorganisms (P. pentosaceus, P. chlororaphis, P. damnosus, B. pumilus, A. aceti, and S. parvus) and four types of thermophilic microorganisms (B. stearothermophilus, S. thermocarboxydus, S. thermospinisporus, and A. sacchari) were found to have high antagonistic activity against the tested pathogenic strains (A. faecalis, B. cinerea, E. carotovora, P. aeruginosa, P. fluorescens, R. stolonifera, X. vesicatoria. pv. Vesicatoria, and E. aphidicola). The introduction of microalgae hydrolyzate increased the concentration of microorganisms by 5.23 times in consortium I, by 4.66 times in consortium II, by 6.6 times in consortium III. These data confirmed the efficiency (feasibility) of introducing microalgae hydrolyzate into the biofertilizer composition.

Enhanced treatment of landfill leachate with cathodic algal biofilm and oxygen-consuming unit in a hybrid microbial fuel cell system

An innovative cathodic algal biofilm microbial fuel cell equipped with a bioactive oxygen consuming unit (AB-OCU-MFC) was proposed for enhancing the leachate treatment containing biorefractory organic matters and high strength of ammonium nitrogen. The proposed AB-OCU-MFC performed better with regard to COD, NH₄⁺-N, TN removals and algal biomass yield than standalone algal biofilm-MFC and control reactors. AB-OCU-MFC with OCU of 2 cm thickness removed more than 86% of COD, 89.4% of NH₄⁺-N, 76.7% of TN and produced a maximum voltage of 0.39 V and biomass productivity of 1.23 g·L^-1·d^-1. The High-throughput sequencing of DNA showed a significant change in microbial community of reactors implemented with OCU, in which the ratio of exoelectrogenic bacteria of anode and denitrifying bacteria on cathode were significantly increased. The results obtained by cathodic algal biofilm MFC with low cost and bioactive barrier of OCU, would provide a new sight for practical application of MFC.