MiDAS 4: A global catalogue of full-length 16S rRNA gene sequences and taxonomy for studies of bacterial communities in wastewater treatment plants

Microbial communities are responsible for biological wastewater treatment, but our knowledge of their diversity and function is still poor. Here, we sequence more than 5 million high-quality, full-length 16S rRNA gene sequences from 740 wastewater treatment plants (WWTPs) across the world and use the sequences to construct the ‘MiDAS 4’ database. MiDAS 4 is an amplicon sequence variant resolved, full-length 16S rRNA gene reference database with a comprehensive taxonomy from domain to species level for all sequences. We use an independent dataset (269 WWTPs) to show that MiDAS 4, compared to commonly used universal reference databases, provides a better coverage for WWTP bacteria and an improved rate of genus and species level classification. Taking advantage of MiDAS 4, we carry out an amplicon-based, global-scale microbial community profiling of activated sludge plants using two common sets of primers targeting regions of the 16S rRNA gene, revealing how environmental conditions and biogeography shape the activated sludge microbiota. We also identify core and conditionally rare or abundant taxa, encompassing 966 genera and 1530 species that represent approximately 80% and 50% of the accumulated read abundance, respectively. Finally, we show that for well-studied functional guilds, such as nitrifiers or polyphosphate-accumulating organisms, the same genera are prevalent worldwide, with only a few abundant species in each genus.Fil: Dueholm, Morten Kam Dahl. Aalborg University; DinamarcaFil: Nierychlo, Marta. Aalborg University; DinamarcaFil: Andersen, Kasper Skytte. Aalborg University; DinamarcaFil: Rudkjøbing, Vibeke. Aalborg University; DinamarcaFil: Knutsson, Simon. Aalborg University; DinamarcaFil: Arriaga, Sonia. Instituto Potosino de Investigación Científica y Tecnológica; MéxicoFil: Bakke, Rune. University College of Southeast Norway; NoruegaFil: Boon, Nico. University of Ghent; BélgicaFil: Bux, Faizal. Durban University of Technology; SudáfricaFil: Christensson, Magnus. Veolia Water Technologies Ab; SueciaFil: Chua, Adeline Seak May. University Malaya; MalasiaFil: Curtis, Thomas P.. University of Newcastle; Reino UnidoFil: Cytryn, Eddie. Agricultural Research Organization Of Israel; IsraelFil: Erijman, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina. Universidad de Buenos Aires; ArgentinaFil: Etchebehere, Claudia. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Fatta Kassinos, Despo. University of Cyprus; ChipreFil: Frigon, Dominic. McGill University; CanadáFil: Garcia Chaves, Maria Carolina. Universidad de Antioquia; ColombiaFil: Gu, April Z.. Cornell University; Estados UnidosFil: Horn, Harald. Karlsruher Institut Für Technologie; AlemaniaFil: Jenkins, David. David Jenkins & Associates Inc; Estados UnidosFil: Kreuzinger, Norbert. Tu Wien; AustriaFil: Kumari, Sheena. Durban University of Technology; SudáfricaFil: Lanham, Ana. University of Bath; Reino UnidoFil: Law, Yingyu. Singapore Centre For Environmental Life Sciences Engineering; SingapurFil: Leiknes, TorOve. King Abdullah University of Science and Technology; Arabia SauditaFil: Morgenroth, Eberhard. Eth Zürich; SuizaFil: Muszyński, Adam. Politechnika Warszawska; PoloniaFil: Petrovski, Steve. La Trobe University; AustraliaFil: Pijuan, Maite. Catalan Institute For Water Research; EspañaFil: Pillai, Suraj Babu. Va Tech Wabag Ltd; IndiaFil: Reis, Maria A. M.. Universidade Nova de Lisboa; PortugalFil: Rong, Qi. Chinese Academy of Sciences; ChinaFil: Rossetti, Simona. Istituto Di Ricerca Sulle Acque (irsa) ; Consiglio Nazionale Delle Ricerche;Fil: Seviour, Robert. La Trobe University; AustraliaFil: Tooker, Nick. University of Massachussets; Estados UnidosFil: Vainio, Pirjo. Espoo R&D Center; FinlandiaFil: van Loosdrecht, Mark. Delft University of Technology; Países BajosFil: Vikraman, R.. VA Tech Wabag, Philippines Inc; FilipinasFil: Wanner, Jiří. University of Chemistry And Technology; República ChecaFil: Weissbrodt, David. Delft University of Technology; Países BajosFil: Wen, Xianghua. Tsinghua University; ChinaFil: Zhang, Tong. The University of Hong Kong; Hong KongFil: Nielsen, Per H.. Aalborg University; DinamarcaFil: Albertsen, Mads. Aalborg University; DinamarcaFil: Nielsen, Per Halkjær. Aalborg University; Dinamarc

Evaluation of fractionation and delignification efficiencies of deep eutectic solvents on oil palm empty fruit bunch

Deep eutectic solvent (DES) has been introduced as a new generation green solvent for lignocellulosic biomass pretreatment in recent years. In the current study, six DES varying from acidic to basic nature were synthesized and applied on oil palm empty fruit bunch (EFB) in a single step fractionation and delignification process. The effect of the properties of DES on its fractionation performance was assessed. Mass balance performed on the pretreatment process reveals that pH of DES has a significant impact on biopolymer fractionation efficiency. The dissolution trend of acidic and basic DES resembles those in the conventional acid and alkaline pretreatments. The pretreatment energy requirement for the DES used ranged from 2087 to 2451 J/g. The acidic choline chloride:lactic acid DES succeeded in achieving 100% hemicellulose extraction, 88% delignification and 50% lignin pellet extraction from EFB. Thus, it is feasible for acidic DES to be considered in a biorefinery scheme for biomass fractionation

Effect of functional groups in acid constituent of deep eutectic solvent for extraction of reactive lignin

In this study, acidic deep eutectic solvents (DES) synthesized from various organic carboxylic acid hydrogen bond donors were applied to lignocellulosic oil palm empty fruit bunch (EFB) pretreatment. The influence of functional group types on acid and their molar ratios with hydrogen bond acceptor on lignin extraction were evaluated. The result showed presence of hydroxyl group and short alkyl chain enhanced biomass fractionation and lignin extraction. Choline chloride:lactic acid (CC-LA) with the ratio of 1:15 and choline chloride:formic acid (CC-FA) with 1:2 ratio extracted more than 60 wt% of lignin. CC-LA DES-extracted lignin (DEEL) exhibited comparable reactivity with technical and commercial lignin based on its phenolic hydroxyl content (3.33–3.72 mmol/glignin). Also, the DES-pretreated EFB comprised of enriched glucan content after biopolymer fractionation. Both DES-pretreated EFB and DEEL can be potential feedstock for subsequent conversion processes. This study presented DES as an effective and facile pretreatment method for reactive lignin extraction. © 201

Transformation of Starchy Lignocellulosic Biomass to Ethanol using Ragi Tapai Synergized with Microwave Irradiation Pretreatment

Ethanol production strategy was studied using multiple strain microbes from microwave irradiation (MI) pretreated sago waste. Sago waste (SW) was MI-pretreated for reducing sugars production using 2 heating media (water and sulfuric acid) under pretreatment conditions including MI power, pretreatment duration, and solid loading. When water was used, the pretreatment parameters were optimized using Box-Behnken Design (BBD). However, gelatinized starch and charring of SW led to an insignificant quadratic model. To mitigate the gelatinization problem while determining the best MI pretreatment conditions, water was substituted by sulfuric acid using single factor method. The highest reducing sugar yield of 261.5 mg/g SW was achieved at 7.5% solid loading, 6 min pretreatment duration, and 300 W MI power. The effectiveness of the pretreatment was ascertained by field-emission scanning electron microscopy (FESEM) and chemical-composition analysis. When fermenting MI-pretreated SW using ragi tapai, simultaneous saccharification of starch and ethanol production was evidenced from the sugar/ethanol profile. A resulted yield of 7.24 g ethanol/100 g SW confirmed the fermentability of MI-pretreated SW. The ethanol production was well fitted into the modified Gompertz model

Comparison of ionic liquid, acid and alkali pretreatments for sugarcane bagasse enzymatic saccharification

Background: Much attention has been given to applying ionic liquids (ILs) as an alternative pretreatment method for lignocellulosic biomass. This study aims to select the most suitable type of IL for pretreating sugarcane bagasse (SCB). The potential of ILs for pretreatment was evaluated and compared with conventional pretreatment media, acids and alkalis. The performance of the pretreatment media was evaluated based on the amount of reducing sugar produced from enzymatic saccharification, the energy requirement, and changes in the chemical structure and crystallinity index of the pretreated bagasse. Results: 1-ethyl-3-methylimidazolium acetate [EMIM]oAc was selected as the most suitable IL for SCB pretreatment. The optimum yields of reducing sugar obtained from [EMIM]oAc-, alkali-, and acid-pretreated SCB were 69.5%, 92.8% and 41.3%, respectively. Although a lower yield of reducing sugar was obtained, [EMIM]oAc pretreatment required the least energy to pretreat 1 kg of SCB. Moreover, the percentage of SCB loss during [EMIM]oAc pretreatment was the lowest. [EMIM]oAc-pretreated SCB also had the lowest crystallinity index (CI) with the most amorphous structure. Conclusion: [EMIM]oAc appears to be another option for pretreating SCB, and other issues such as the recyclability of [EMIM]oAc is worth investigating. © 2011 Society of Chemical Industry

Enrichment of PHA-accumulators for sustainable PHA production from crude glycerol

Polyhydroxyalkanoates (PHAs) as biodegradable polymers produced by microorganisms with thermo-plastic properties are of high interest. In this study, PHA-accumulators were cultivated using crude glycerol and activated sludge in a sequencing batch reactor (SBR) with the aerobic dynamic feeding (ADF) strategy. This study aimed to enrich PHA-accumulators by evaluating the stability of the cultivation reactor followed by the effect of organic loading rate (OLR). The cultivation reactor was stable while maintaining a steady feast/famine (F/F) ratio. The increase of OLR from 360 mgC/(L·d) to 1000 mgC/(L·d) led to the increment of biomass concentration from less than 0.7 g/L to 2 g/L. The enriched mixed culture produced a maximum PHA content of 80 wt% in biomass dry weight with a production yield of 0.7 mg C PHA/mg C. The mixed culture were found to accumulate both 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3 HV) monomers at a HB:HV molar ratio of 60:40. Based on fluorescence in situ hybridization (FISH) analysis, Alphaproteobacteria and Betaproteobacteria were the most dominant species during peak PHA production. This method provides an option for resource recovery operation in converting waste to value-added products

The microbial community in a high-temperature enhanced biological phosphorus removal (EBPR) process

An enhanced biological phosphorus removal (EBPR) process operated at a relatively high temperature, 28 °C, removed 85% carbon and 99% phosphorus from wastewater over a period of two years. This study investigated its microbial community through fluorescent in situ hybridization (FISH) and clone library generation. Through FISH, considerably more Candidatus “Accumulibacter phosphatis” (Accumulibacter)-polyphosphate accumulating organisms (PAOs) than Candidatus ‘Competibacter phosphatis’ (Competibacter)-glycogen accumulating organisms were detected in the reactor, at 36 and 7% of total bacterial population, respectively. A low ratio of Glycogen/Volatile Fatty Acid of 0.69 further indicated the dominance of PAOs in the reactor. From clone library generated, 26 operational taxonomy units were retrieved from the sludge and a diverse population was shown, comprising Proteobacteria (69.6%), Actinobacteria (13.7%), Bacteroidetes (9.8%), Firmicutes (2.94%), Planctomycetes (1.96%), and Acidobacteria (1.47%). Accumulibacter are the only recognized PAOs revealed by the clone library. Both the clone library and FISH results strongly suggest that Accumulibacter are the major PAOs responsible for the phosphorus removal in this long-term EBPR at relatively high temperature

Process intensification of cellulase and bioethanol production from sugarcane bagasse via an integrated saccharification and fermentation process

The production of value-added products such as cellulase and ethanol via a consolidated bioprocess could be realized by tapping into the multiple actions of a microbial community. For this purpose, an in situ saccharification and fermentation process through a sequential co-culture white-rot fungus and Saccharomyces cerevisiae on NaOH-pretreated sugarcane bagasse (SCB) was investigated. In the present work, white rot fungus plays a role in the production of cellulase enzymes. With the produced cellulase, an in situ saccharification process took place in the reactor to depolymerize pretreated SCB into reducing sugar. The reducing sugar was converted into ethanol via fermentation by S. cerevisiae, which was added into the system sequentially. White rot fungus Pycnoporus sanguineus was selected due to its competency in producing cellulase and reducing sugar production. The operating condition to maximize the production of reducing sugar in situ was obtained through a Central Composite Design method. A total of 3.13 g reducing sugar/100 g SCB was obtained when P. sanguineus was cultivated at 0.6% inoculum loading, 70% moisture content and 4 days. Subsequently, 4.5 g ethanol/100 g SCB was obtained from the in situ saccharification and fermentation system after S. cerevisiae was sequentially inoculated