Anaerobic digestion of organic waste into methane and carbon dioxide (biogas) is carried out by complex microbial communities. Here, we use full-length 16S rRNA gene sequencing of 285 full-scale anaerobic digesters (ADs) to expand our knowledge about diversity and function of the bacteria and archaea in ADs worldwide. The sequences are processed into full-length 16S rRNA amplicon sequence variants (FL-ASVs) and are used to expand the MiDAS 4 database for bacteria and archaea in wastewater treatment systems, creating MiDAS 5.
View Article and Find Full Text PDFThe scope of the current study was to investigate the efficiency of a two-stage anaerobic-aerobic process for the simultaneous treatment and valorization of selective wastewater streams from a confectionary industry. The specific wastewater (confectionary industry wastewater, CIW) was a mixture of the rinsing eluting during washing of the cauldrons in which jellies and syrups were produced, and contained mainly readily fermentable sugars, being thus of high organic load. The first stage of the process was the dark fermentation (DF) of the CIW in continuous, attached-biomass systems, in which the effect on hydrogen yields and distribution of metabolites were studied for different packing materials (ceramic or plastic), hydraulic retention times, HRTs (12 h-30 h) and feed substrate concentration (20 g COD/L- 50 g COD/L).
View Article and Find Full Text PDFThis study deals with the effect of different organic loading rates (OLRs) on the organic load removal and the productivity of methane, in a microbial electrolysis cell-anaerobic digestion (MEC-AD) system treating raw waste activated sludge (WAS). For comparison, two identical reactors, a control (AD) and a MEC-AD reactor were constructed. Both reactors operated for 131 days, during which different Organic Loading Rates (OLRs) were examined; 1.
View Article and Find Full Text PDFAs an easily obtained organic waste, by-product acetic acid could be an appropriate co-substrate with blue algae wastes (increase C/N ratio of substrates) for co-fermentation of PHA production. However, there are still acrylic acid and other chemicals in by-product acetic acid, which could cause severe inhibition for fermenting microorganisms during PHA production process. The current study represented that alkali pretreatment (pH level of 12) is a more favorable method compared with thermal pretreatment (80 ℃ for 30 min) for breaking cell walls of blue algae.
View Article and Find Full Text PDFInt J Biol Macromol
January 2023
In the current study, a mixed microbial culture (MMC) of polyhydroxyalkanoates (PHAs) producers was developed under nutrient stress and was assessed as biocatalyst for the production of high-yielding PHAs from fermented (acidified) discarded fruit juices (DFJ). The structure of the MMC was analyzed periodically to determine its microbial dynamics, revealing that Zoogloae sp. dominated throughout the operation of the system.
View Article and Find Full Text PDFPHAs are a form of cellular storage polymers with diverse structural and material properties, and their biodegradable and renewable nature makes them a potential green alternative to fossil fuel-based plastics. PHAs are obtained through extraction via various mechanical, physical and chemical processes after their intracellular synthesis. Most studies have until now focused on pure cultures, while information on mixed microbial cultures (MMC) remains limited.
View Article and Find Full Text PDFThe effect of different pretreatment approaches based on alkali (NaOH)/hydrogen peroxide (HO) on willow sawdust (WS) biomass, in terms of delignification efficiency, structural changes of lignocellulose and subsequent fermentation toward ethanol, was investigated. Bioethanol production was carried out using the conventional yeast as well as three non-conventional yeasts strains, i.e.
View Article and Find Full Text PDFDark fermentation (DF) of several types of wastes is a promising process to alleviate environmental pollution as it leads to the production of valuable hydrogen (H) gas and high added value products, such as volatile fatty acids (VFAs). In this study a kinetic model for fermentative H production in an Up-flow column reactor (UFCR) is presented. Τhe model structure includes seven biochemical reactions taking place in a two-phase biofilm-liquid system.
View Article and Find Full Text PDFGiven that the social and economic sustainability of rural areas is highly based on the protection of natural resources, biodiversity and human health, simple-operated and cost-effective wastewater treatment systems, like artificial constructed wetlands (CWs), are widely proposed for minimizing the environmental and human impact of both water and soil pollution. Considering that the optimization of wastewater treatment processes is vital for the reduction of effluents toxic potential, there is imperative need to establish appropriate management strategies for ensuring CW performance and operational efficiency. To this end, the present study aimed to assess the operational efficiency of a horizontal free water surface CW (HFWS-CW) located in a world heritage area of Western Greece, via a twelve-month duration Toxicity Identification Evaluation (TIE)-like approach, including both chemical and biological tracking tools.
View Article and Find Full Text PDFBiohydrogen using migrated ammonia as nitrogen source, and biogas upgrading with hydrogen collected at biocathode in an integrated bioelectrochemical system (BES) were investigated, during the anaerobic digestion of Taihu blue algae. Under an applied voltage of 0.4 V, biohydrogen (202.
View Article and Find Full Text PDFThe objective of the current work is to study the impact of the operational parameters' variation (HRT, OLR and T) on biomethane productivity in a periodic anaerobic baffled reactor (PABR). The feedstock used was a biomass product named food residue biomass (FORBI), which is dried and shredded source-separated household food waste. The PABR is an innovative, high-rate bioreactor.
View Article and Find Full Text PDFFour multiple air-cathode microbial fuel cells (MFCs) were developed under the scope of using extracts from fermentable household food waste (FORBI) for the production of bioelectricity. The operation of the MFCs was assessed in batch mode, considering each cell individually. Τhe chemical oxygen demand (COD) efficiency was relatively high in all cases (>85% for all batch cycles) while the electricity yield was 20 mJ/gCOD/L of extract solution.
View Article and Find Full Text PDFThe scope of this paper is to examine the environmental and economic performance of an alternative household fermentable waste (HFW) management paradigm, developed within the framework of the HORIZON 2020 project Waste4think. In Greece, the business-as-usual scheme for the management of HFW is its disposal in landfills as part of mixed waste. Waste4think developed an alternative approach based on the benefits of source separation.
View Article and Find Full Text PDFA pilot assessment procedure is introduced and used for the self-heating behavior of 50 industrial wastes based on UN N. 4 test and their subsequent classification as hazardous or non-hazardous, according to the Waste Framework Directive (WFD). When a waste contains self-heating substances it is classified as 'Hazardous Waste' by hazard property HP3: Flammable according to Regulation (EU) No 1357/2014.
View Article and Find Full Text PDFThe present study investigated the effect of thermo-chemical pretreatment on the enhancement of enzymatic digestibility of olive mill stones (OMS), as well as its possible valorisation via bioconversion of the generated free sugars to alcohols. Specifically, the influence of parameters such as reaction time, temperature, type and concentration of dilute acids and/or bases, was assessed during the thermo-chemical pretreatment. The hydrolysates and the solids remaining after pretreatment, as well as the whole pretreated slurries, were further evaluated as potential substrates for the simultaneous production of ethanol and xylitol via fermentation with the yeast Pachysolen tannophilus.
View Article and Find Full Text PDFGas fermentation for the production of building block molecules and biofuels is lately gaining attention as a means to eliminate the greenhouse gases emissions. Especially CO capture and recycling are in focus. Thus, the biological coupling of CO and H is of high interest.
View Article and Find Full Text PDFIn the present study the bioconversion of dried household food waste (FORBI) to energy carriers was investigated aiming to its sustainable management and valorization. FORBI was either directly fermented towards ethanol and hydrogen or was previously subjected to extraction with water resulting to a liquid fraction (extract) rich in sugars and a solid residue, which were then fermented separately. Subsequently, the effluents were assessed as substrates for methane production via anaerobic digestion (AD).
View Article and Find Full Text PDFVarious pretreatment methods, such as thermal, alkaline and acid, were applied on grass lawn (GL) waste and the effect of each pretreatment method on the Biochemical Methane Potential was evaluated for two options, namely using the whole slurry resulting from pretreatment or the separate solid and liquid fractions obtained. In addition, the effect of each pretreatment on carbohydrate solubilization and lignocellulossic content fractionation (to cellulose, hemicellulose, lignin) was also evaluated. The experimental results showed that the methane yield was enhanced with alkaline pretreatment and, the higher the NaOH concentration (20 g/100 gTotal Solids (TS)), the higher was the methane yield observed (427.
View Article and Find Full Text PDFThe present study focuses on the exploration of the potential use of potato peels waste (PPW) as feedstock for bioethanol production, using a newly isolated yeast strain, Wickerhamomyces anomalus, via different saccharification and fermentation schemes. The saccharification of PPW was performed via thermal and chemical (acid, alkali) pretreatment, as well as via enzymatic hydrolysis through the use of commercial enzymes (cellulase and amylase) or enzymes produced at lab scale (alpha-amylase from Bacillus sp. Gb67), either separately or in mixtures.
View Article and Find Full Text PDFThe present study focuses on the production of an alternative fuel (AF) for the cement industry from a food residue biomass (FORBI) product, generated from pre-sorted household food waste (HFW). FORBI is generated by drying and shredding the fermentable fraction of HFW collected door-to-door in the Municipality of Halandri, Greece. The key physicochemical properties such as the net calorific value (NCV), and the concentration of heavy metals and chlorine are subsequently determined using well-established international standards (EN and ISO).
View Article and Find Full Text PDFHousehold food waste management and treatment has been recognised as a significant issue worldwide and at a European Union level. Source-separation of household food waste following drying at source presents a viable solution to this problem. The present research aims at investigating the effect of drying of model household food waste at different temperatures (i.
View Article and Find Full Text PDFIn this study, the use of a dual-chamber microbial fuel cell for the production of bioelectricity from a food residue biomass (FORBI) product was investigated. Food residue biomass was produced by drying and shredding the pre-sorted fermentable fraction of household food waste collected door-to-door in the Municipality of Halandri, Athens, Greece. Different organic loads of food residue biomass expressed as chemical oxygen demand (COD) were examined (0.
View Article and Find Full Text PDFA combined Lewis-Brønsted acid ethanolysis of sugars was thoroughly investigated with the aim of producing ethyl levulinate (EL) in a single step. Ethanolysis carried out at 453 K for 4 h using HSO (1 wt%) and AlCl·6HO (30 mol % with respect to sugars) produced a yield of 60 mol % of EL respect to glucose and starch. Such optimised conditions were positively applied directly on different food waste, preliminarily characterised and found to be mainly composed by simple (10-15%) and relatively complex sugars (20-60%), besides proteins (6-10%) and lipids (4-10%), even in their wet form.
View Article and Find Full Text PDFThe biotransformation of the pre-dried and shredded organic fraction of kitchen waste to ethanol was investigated, via co-cultures of the yeasts Saccharomyces cerevisiae and Pichia stipitis (Scheffersomyces stipitis). Preliminary experiments with synthetic media were performed, in order to investigate the effect of different operational parameters on the ethanol production efficiency of the co-culture. The control of the pH and the supplementation with organic nitrogen were shown to be key factors for the optimization of the process.
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