Microaerobic Conditions Research Articles

Isolation and Characterization of Facultative-Anaerobic Antimonate-Reducing Bacteria.

Microbial antimonate (Sb(V)) reduction is a promising approach to remove Sb(V) from wastewater. However, current knowledge regarding microbial Sb(V) reduction is limited to strictly anaerobic conditions. This study was the first to isolate three facultative-anaerobic Sb(V)-reducing bacterial strains from the sludge collected from a wastewater treatment facility in an antimony products plant. Two of the isolated strains, designated Dechloromonas sp. AR-2 and Propionivibrio sp. AR-3, were characterized based on their Sb(V)-reducing abilities. When cultivated under anaerobic conditions with Sb(V) and acetate as the electron acceptor and donor, respectively, both strains could efficiently reduce 5.0 mM Sb(V), removing most of it from the water phase within 7 d. Along with Sb(V) reduction by the strains, white precipitates, which were likely amorphous Sb(OH)3 solids, were formed with a minor generation of soluble antimonite. Additionally, respiratory Sb(V) reduction by both strains occurred not only under anaerobic but also microaerobic conditions. It was suggested that Sb(V) reduction and the growth abilities of the strains under microaerobic conditions presented a substantial advantage of the use of strains AR-2 and AR-3 for practical applications to Sb(V)-containing wastewater treatment.

Effect of dissolved oxygen concentration (microaerobic and aerobic) on community structure and activity of culturable heterotrophic nitrifying bacteria in activated sludge

ABSTRACT To investigate the community structures and heterotrophic nitrifying activities of culturable heterotrophic nitrifying bacteria (HNB) in activated sludge, two sludge samples, cultivated at aerobic (2.5–4.0 mg·L−1 dissolved oxygen) and microaerobic conditions (0.5–1.0 mg·L−1 dissolved oxygen) respectively, were analyzed by isolation, purification, sequencing, and phylogenetic analysis. Ultimately, 48 and 50 effective 16S rDNA sequences (representing >80% of the total colonies on an agar plate) were collected from the two samples, from which seven and eight operational taxonomic units (OTUs) were obtained, respectively. All OTU-identified isolates showed typical heterotrophic nitrification, including six reported and six previously undescribed HNB species. The two culturable HNB 16S rDNA sequence libraries exhibited significant differences in the diversity and relative abundance of culturable HNB species. The microaerobic conditions encouraged a more diverse culturable HNB community in activated sludge compared to aerobic conditions.

Engineering Escherichia coli for Direct Production of 1,2-Propanediol and 1,3-Propanediol from Starch.

Diols are versatile chemicals used for multiple manufacturing products. In some previous studies, Escherichia coli has been engineered to produce 1,2-propanediol (1,2-PDO) and 1,3-propanediol (1,3-PDO) from glucose. However, there are no reports on the direct production of these diols from starch instead of glucose as a substrate. In this study, we directly produced 1,2-PDO and 1,3-PDO from starch using E. coli engineered for expressing a heterologous α-amylase, along with the expression of 1,2-PDO and 1,3-PDO synthetic genes. For this, the recombinant plasmids, pVUB3-SBAharboring amyA gene for α-amylase production, pSR5 harboring pct, pduP, and yahK genes for 1,2-PDO production, and pSR8 harboring gpd1-gpp2, dhaB123, gdrAB, and dhaT genes for 1,3-PDO production, were constructed. Subsequently, E. coli BW25113 (ΔpflA) and BW25113 strains were transformed with pVUB3-SBA, pSR5, and/or pSR8. Using these transformants, direct production of 1,2-PDO and 1,3-PDO from starch was demonstrated under microaerobic condition. As a result, the maximum production titers of 1,2-PDO and 1,3-PDO from 1% glucose as a sole carbon source were 13mg/L and 150mg/L, respectively. The maximum production titers from 1% starch were similar levels (30mg/L 1,2-PDO and 120mg/L 1,3-PDO). These data indicate that starch can be an alternative carbon source for the production of 1,2-PDO and 1,3-PDO in engineered E. coli. This technology could simplify the upstream process of diol bioproduction.

Strain engineering for high-level 5-aminolevulinic acid production in Escherichia coli.

Herein, we report the development of a microbial bioprocess for high-level production of 5-aminolevulinic acid (5-ALA), a valuable non-proteinogenic amino acid with multiple applications in medical, agricultural, and food industries, using Escherichia coli as a cell factory. We first implemented the Shemin (i.e., C4) pathway for heterologous 5-ALA biosynthesis in E. coli. To reduce, but not to abolish, the carbon flux toward essential tetrapyrrole/porphyrin biosynthesis, we applied clustered regularly interspersed short palindromic repeats interference (CRISPRi) to repress hemB expression, leading to extracellular 5-ALA accumulation. We then applied metabolic engineering strategies to direct more dissimilated carbon flux toward the key precursor of succinyl-CoA for enhanced 5-ALA biosynthesis. Using these engineered E. coli strains for bioreactor cultivation, we successfully demonstrated high-level 5-ALA biosynthesis from glycerol (~30 g L-1 ) under both microaerobic and aerobic conditions, achieving up to 5.95 g L-1 (36.9% of the theoretical maximum yield) and 6.93 g L-1 (50.9% of the theoretical maximum yield) 5-ALA, respectively. This study represents one of the most effective bio-based production of 5-ALA from a structurally unrelated carbon to date, highlighting the importance of integrated strain engineering and bioprocessing strategies to enhance bio-based production.

Tichowtungia aerotolerans gen. nov., sp. nov., a novel representative of the phylum Kiritimatiellaeota and proposal of Tichowtungiaceae fam. nov., Tichowtungiales ord. nov. and Tichowtungiia class. nov.

Kiritimatiellaeota is widespread and ecologically important in various anoxic environments. However, the portion of culturable bacteria within this phylum is quite low and, in fact, there is only one currently described species. In this study, a novel anaerobic, non-motile, coccoid, Gram-stain-negative bacterial strain, designated S-5007T, was isolated from surface marine sediment. The 16S rRNA gene sequence was found to have very low 16S rRNA gene sequence similarity to the nearest known type strain, Kiritimatiella glycovorans L21-Fru-ABT (84.9 %). The taxonomic position of the novel isolate was investigated using a polyphasic approach and comparative genomic analysis. Phylogenetic analyses based on 16S rRNA genes and genomes indicated that strain S-5007T branched within the radiation of the phylum Kiritimatiellaeota. Different from the type strain, strain S-5007T can grow under microaerobic conditions, and the genomes of strain S-5007T and the other strains in its branch have many more antioxidant-related genes. Meanwhile, other different metabolic features deduced from genome analysis supported the separate evolution of the proposed class (strain S-5007T branch) and K. glycovorans L21-Fru-ABT. Based on phylogenetic and phenotypic characterization studies, Tichowtungia aerotolerans gen. nov., sp. nov. is proposed with S-5007T (=MCCC 1H00402T=KCTC 15876T) as the type strain, as the first representative of novel taxa, Tichowtungiales ord. nov., Tichowtungiaceae fam. nov. in Tichowtungiia class. nov.

Can microaeration boost the biotransformation of parabens in high-rate anaerobic systems?

The main objective of the present study was to demonstrate microaeration as an effective strategy to boost the biotransformation of four parabens (methylparaben, ethylparaben, propylparaben, and butylparaben) in an upflow anaerobic sludge blanket reactor operated at a short hydraulic retention time (8 h). Moreover, the effect of different airflow rates (1−4 mL min−1) was also assessed from an engineering and microbiological perspective. Low mean removal efficiencies (REs) (14–20 %) were achieved under anaerobic conditions. However, the addition of only 1mL air min−1 (0.027L O2L−1 feed) remarkably boosted the biotransformation of parabens, ensuring mean REs above 85 % for all compounds. In contrast, the increase in the airflow rate had a minor impact on the process, and an apparent saturation in the removal capacity was observed, noticeably from 2 to 4 mL air min−1. The reactor presented high stability throughout the experiment, and microaeration did not impair the organic matter removal and methanogenesis. However, high airflow rates can dilute biogas, compromising its use as a fuel in combined heat and power units. The microaerobic conditions increased both richness and diversity of the reactor’s microbiota, likely favoring the growth of oxygenase-producing microorganisms, which may have played a role in the biotransformation of parabens. Finally, the high REs of parabens reached in the microaerated reactor, a more cost-effective technology, are comparable to those found in high-cost wastewater treatment systems, such as activated sludge and its variants.

Nitrogen removal from landfill leachate by single-stage anammox and partial-nitritation process: effects of microaerobic condition on performance and microbial activities

Nitrogen levels in landfill leachate (LL) could potentially pollute water bodies and surrounding groundwater, when discharged untreated. Against this backdrop, pollutant removal from leachate generated at landfill sites is essential. However, a cost-efficient approach, which could concurrently remove various pollutants within LL via single-stage approach, and under microaerobic conditions, has not been fully explored. In this study, single-stage nitrogen removal using anammox and partial-nitritation (SNAP) process was proposed and employed to treat LL under microaerobic condition in an upflow sludge blanket. When reactor dissolved oxygen-(DO) of 0.2 mg/L was implemented along with nitrogen loading rate-(NLR) ranging 0.31-1.84 kg/m3·d, 99.5% NH4+-N, 94.3% TN and 31.04% chemical oxygen demand (COD) removals was concurrently achieved. Conversely, when DO was elevated to 0.6 mg/L, nitrogen removal was curtailed to <20%, NO2--N accumulation reached 98.68%, indicating inhibition of anammox bacterial (AmxB) activities. 16S-rRNA-high-throughput gene sequencing revealed ammonium oxidizing bacteria-[AOB] (Nitrosomonas and Sphingomonas), AmxB (Candidatus Kuenenia), heterotrophic denitrifiers-[HDB] (Comamonas, Dechloromonas), and COD degrading bacteria (Bellilinea, Ignavibacterium) as the dominant genera which coordinated synergistic activities to establish the SNAP process and led to the single-stage pollutants removal from the LL. Sludge morphological revealed by SEM and energy-dispersive X-ray spectroscopy indicated that reactor sludge comprised of granulated sludge, and was noticeably embedded in extracellular polymeric substances (EPS), an indication of a defense mechanism initiated by microbes against heavy metals toxicity. The SNAP process demonstrated a promising cost-efficient simultaneous nitrogen and carbon removal from LL.

Enhanced Biosynthesis of Plasmid DNA from Escherichia coli Applying Experimental Design.

Therapeutic applications of plasmid DNA (pDNA) have significantly advanced during the last years. Currently, several pDNA-based drugs are already in the market, whereas several others have entered phases 2 and 3 of clinical trials. The present and future demand for pDNA requires the development of efficient bioprocesses to produce it. Commonly, pDNA is produced by cultures of Escherichia coli. It has been previously demonstrated that specific strains of E. coli with a modified substrate transport system can be able to attain high cell densities in batch mode, due to the very low overflow metabolism displayed. However, the large amounts of oxygen demanded can lead to microaerobic conditions after some hours of cultivation, even at small scale. Typically, the inherent problems for these cultures are the high oxygen demand and the accumulation of acetate, a metabolic byproduct that is synthesized aerobically when the glucose rate exceeds the limits.In recent years, several researches have been focused on the study of induction of plasmid DNA as well as strategies for fermentation using semi-defined mediums. These studies conceived relevant results that allow us to design a production platform for enhanced plasmid DNA. So, the main goal of this chapter is to show how the development of an experimental design directed to aromatic amino acids pathway can improve the yield of a therapeutic plasmid DNA by culture of a new strain of Escherichia coli VH33.

Analysis of ethanol production from xylose using Pichia stipitis in microaerobic conditions through experimental observations and kinetic modelling

Hydrolysis of biomass (e.g. bagasse) leads to xylose as one of the primary sugars for fermentation to bioethanol, along with glucose. The selection of a suitable microorganism and consequently selection of suitable aeration levels for the selected microorganism plays a significant role in xylose conversion. This work focuses on the kinetics of bioethanol production from xylose using Pichia stipitis with the development of a MATLAB mathematical model (based on the combined Andrews and Levenspiel's model with oxygen limitation and inhibition terms included), considering the effects of substrate, oxygen, biomass and product concentrations on sugar utilisation, growth rate and ethanol formation. Experiments were carried out to validate the kinetic model under anaerobic and microaerobic growth conditions in a batch process. The results showed good correlation with an average R2 of 0.92 for bioethanol production, 0.95 for xylose consumption and 0.83 for biomass growth. Different aeration levels of 0.0, 0.1 and 0.2 vvm and different initial biomass concentrations of 0.3, 1.5 and 3 g L-1 were tested, in which the combination of aeration at 0.1 vvm and a biomass concentration of 3 g L-1 resulted in the highest ethanol yield and productivity of 0.45 g g-1 and 0.75 g L-1 h-1 respectively.

Comparative assessment of growth media and incubation conditions for enhanced recovery and isolation of Acinetobacter baumannii from aquatic matrices

Acinetobacter baumannii causes serious multidrug resistant nosocomial infections around the world. This comprehensive comparative study was designed to assess the effect of temperature (30, 37 and 42 °C), incubation (aerobic and microaerobic) condition and selective [CHROMagar Acinetobacter (CHR) and Leeds Acinetobacter Medium (LAM)] and non-selective [Modified Karmali Agar (MKA)] growth media on the enhanced recovery of A. baumannii from a variety of water (agricultural, recreational, raw drinking intake source, pre-chlorinated and post-chlorinated wastewater effluent) samples spiked with a known number of A. baumannii cells. After spiking each water type with a known number of cells in 10 mL volume, the sample was passed through a membrane filter (pore size 0.45 μm) and filters were placed on different selective media plates and subjected to incubate at various incubation conditions. The results reported in this study show that for all water types tested (except post-chlorinated wastewater effluent), LAM was the most effective selective growth medium in combination with variable temperature and incubation conditions for yielding high recovery rates of A. baumannii cells. Overall, A. baumannii showed that it has a high adaptive capacity to grow on selective and non-selective growth media at different temperature and incubation conditions. The data described in this study suggest that no single incubation condition and growth media would efficiently recover A. baumannii from all environmental water types tested. This data also indicate that selective growth media and incubation condition can significantly affect the recovery of A. baumannii. Differences in recovery of A. baumannii observed in this study which appeared to be dependent on the temperature and environmental characteristics of incubation as well as the sample type, suggest the need for caution when comparing recovery using different protocols.

The potential use of purple nonsulfur bacteria to simultaneously treat chicken slaughterhouse wastewater and obtain valuable plant growth promoting effluent and their biomass for agricultural application

Abstract Treatment of wastewater with purple nonsulfur bacteria (PNSB) simultaneously produces the biomass of plant growth promoting bacteria (PGPB) and the effluent containing plant growth promoting substances (PGPS). Among 46 PNSB strains isolated from chicken slaughterhouse wastewater (CSW) treatment unit, only four strains grew well in non-sterile effluent of the anaerobic digester (CSW-Di), under both microaerobic light and aerobic dark conditions. However, only strains WS308 and WS502 were selected as inoculants for subsequent experiments since they released high levels of 5-aminolevulinic acid (ALA) into the digester effluent medium under both incubating conditions. Based on 16S rRNA genes analysis, the strains WS308 and WS502 were identified as Rhodopseudomonas faecalis and Rhodopseudomonas palustris, respectively. The central composite design (CCD) experiments were conducted by using a mixed culture of the two strains (1:1) treating the non-sterile CSW-Di (soluble chemical oxygen demand, sCOD 736 mg/L) under 72-hr microaerobic light condition. The optimal conditions on the multivariate regression were found at the inoculum size (X1) of 3.63% (roughly 106 cells/mL), initial pH (X2) of 6.9 and light intensity (X3) of 3731 lux. At this condition, sCOD removal was predicted at 85.3%, while the verification test result favorably achieved 88.1% removal. ALA concentration in CSW-Di of the verification set was found at 0.13 mg/L. All trace elements detected in CSW-Di effluent were much lower than recommended maximum concentrations for irrigation water. Treating wastewater with potent PNSB strains could produce effluent containing PGPS, such as ALA, and also the biomass as PGPB for organic agricultural applications.

Occurrence, Virulence and Antimicrobial Resistance-Associated Markers in Campylobacter Species Isolated from Retail Fresh Milk and Water Samples in Two District Municipalities in the Eastern Cape Province, South Africa.

Campylobacter species are among the major bacteria implicated in human gastrointestinal infections and are majorly found in faeces of domestic animals, sewage discharges and agricultural runoff. These pathogens have been implicated in diseases outbreaks through consumption of contaminated milk and water in some parts of the globe and reports on this is very scanty in the Eastern Cape Province. Hence, this study evaluated the occurrence as well as virulence and antimicrobial-associated makers of Campylobacter species recovered from milk and water samples. A total of 56 water samples and 72 raw milk samples were collected and the samples were processed for enrichment in Bolton broth and incubated for 48 h in 10% CO2 at 42 °C under microaerobic condition. Thereafter, the enriched cultures were further processed and purified. After which, presumptive Campylobacter colonies were isolated and later confirmed by PCR using specific primers for the detection of the genus Campylobacter, target species and virulence associated genes. Antimicrobial resistance profiles of the isolates were determined by disk diffusion method against a panel of 12 antibiotics and relevant genotypic resistance genes were assessed by PCR assay. A total of 438 presumptive Campylobacter isolates were obtained; from which, 162 were identified as belonging to the genus Campylobacter of which 36.92% were obtained from water samples and 37.11% from milk samples. The 162 confirmed isolates were further delineated into four species, of which, 7.41%, 27.16% and 8.64% were identified as C. fetus, C. jejuni and C. coli respectively. Among the virulence genes screened for, the iam (32.88%) was most prevalent, followed by flgR (26.87%) gene and cdtB and cadF (5.71% each) genes. Of the 12 antibiotics tested, the highest phenotypic resistance displayed by Campylobacter isolates was against clindamycin (95.68%), while the lowest was observed against imipenem (21.47%). Other high phenotypic resistance displayed by the isolates were against erythromycin (95.06%), followed by ceftriaxone (93.21%), doxycycline (87.65%), azithromycin and ampicillin (87.04% each), tetracycline (83.33%), chloramphenicol (78.27%), ciprofloxacin (77.78%), levofloxacin (59.88%) and gentamicin (56.17%). Relevant resistance genes were assessed in the isolates that showed high phenotypic resistance, and the highest resistance gene harbored by the isolates was catII (95%) gene while VIM, KPC, Ges, bla-OXA-48-like, tetC, tetD, tetK, IMI and catI genes were not detected. The occurrence of this pathogen and the detection of virulence and antimicrobial resistance-associated genes in Campylobacter isolates recovered from milk/water samples position them a risk to human health.

Xylose 기질을 소모하는 재조합 Saccharomyces cerevisiae의 lactic acid 생산수율 향상을 위한 조건 탐색

Lactic acid is widely used in the food, pharmaceutical, textile and chemical industries. Also, poly-lactic acid (PLA) is in increasing demand as an environmentally friendly and biodegradable plastic. In our prior study, a lactic acid-producing, xylose-fermenting Saccharomyces cerevisiae strain (SR8 LDH) has been developed. In the present study, we tested the SR8 LDH strain under various fermentation conditions to discover the most important condition determining lactic acid and ethanol production profiles. Using xylose as a substrate significantly improved lactic acid yields compared to using glucose under microaerobic conditions. High initial cell density improved lactic acid productivity, but it did not affect ethanol production. Lastly, when fermenting xylose, the PDC1 gene encoding pyruvate decarboxylase was transcriptionally repressed, which might be associated with the production of low ethanol and high lactic acid. These results indicate that the type of a carbon source, i.e. using xylose instead of glucose could be a promising solution for lactic acid production by engineered S. cerevisiae.

Preliminary Study on Microbial Desulfurization: Targeting H2S Removal from Biogas with a Bioscrubber

Bio-desulfurization generally involves the oxidation of sulfide to sedimented, sulfur compounds in microaerobic conditions and is applied at biogas power plants by the palm oil industry. In this wo...

Effect of oxygen limitation on the enrichment of bacteria degrading either benzene or toluene and the identification of Malikia spinosa (Comamonadaceae) as prominent aerobic benzene-, toluene-, and ethylbenzene-degrading bacterium: enrichment, isolation and whole-genome analysis

The primary aims of this present study were to evaluate the effect of oxygen limitation on the bacterial community structure of enrichment cultures degrading either benzene or toluene and to clarify the role of Malikia-related bacteria in the aerobic degradation of BTEX compounds. Accordingly, parallel aerobic and microaerobic enrichment cultures were set up and the bacterial communities were investigated through cultivation and 16S rDNA Illumina amplicon sequencing. In the aerobic benzene-degrading enrichment cultures, the overwhelming dominance of Malikia spinosa was observed and it was abundant in the aerobic toluene-degrading enrichment cultures as well. Successful isolation of a Malikia spinosa strain shed light on the fact that this bacterium harbours a catechol 2,3-dioxygenase (C23O) gene encoding a subfamily I.2.C-type extradiol dioxygenase and it is able to degrade benzene, toluene and ethylbenzene under clear aerobic conditions. While quick degradation of the aromatic substrates was observable in the case of the aerobic enrichments, no significant benzene degradation, and the slow degradation of toluene was observed in the microaerobic enrichments. Despite harbouring a subfamily I.2.C-type C23O gene, Malikia spinosa was not found in the microaerobic enrichments; instead, members of the Pseudomonas veronii/extremaustralis lineage dominated these communities. Whole-genome analysis of M. spinosa strain AB6 revealed that the C23O gene was part of a phenol-degrading gene cluster, which was acquired by the strain through a horizontal gene transfer event. Results of the present study revealed that bacteria, which encode subfamily I.2.C-type extradiol dioxygenase enzyme, will not be automatically able to degrade monoaromatic hydrocarbons under microaerobic conditions.

Methane and hydrogen production from cotton waste by dark fermentation under anaerobic and micro-aerobic conditions

The dark fermentation (DF) of organic textile (e.g. cotton) wastes is discussed in this paper. The influence of micro-aeration on hydrogen and methane production is studied. Fermentation was carried out under the following conditions: load 5 g VSS/L (Volatile Suspended Solids), the pH was varied in the range from 6.23 to 7.8; oxygen was added in small quantities. The oxygen flow rates (OFRs) were varied between 1 and 4.6 mL/h. The highest yields of methane (0.78 L/g VSS) were obtained under anaerobic conditions and neutral pH (7.54), while the production of hydrogen (1.1 mL/g VSS) peaked under an oxygen flow rate of 4.6 mL/h and a pH value of 6.4. Hydrogen and methane yield and the peak days of their production from various substrates (such as cotton waste, sour cabbage, wheat straw, and potato wastes) were compared and discussed. Cotton waste is a potential source of methane, but is substantially less efficient than potato waste.

Impact of Electron Acceptor Availability on Methane-Influenced Microorganisms in an Enrichment Culture Obtained From a Stratified Lake.

Methanotrophs are of major importance in limiting methane emissions from lakes. They are known to preferably inhabit the oxycline of stratified water columns, often assumed due to an intolerance to atmospheric oxygen concentrations, but little is known on the response of methanotrophs to different oxygen concentrations as well as their preference for different electron acceptors. In this study, we enriched a methanotroph of the Methylobacter genus from the oxycline and the anoxic water column of a stratified lake, which was also present in the oxic water column in the winter. We tested the response of this Methylobacter-dominated enrichment culture to different electron acceptors, i.e., oxygen, nitrate, sulfate, and humic substances, and found that, in contrast to earlier results with water column incubations, oxygen was the preferred electron acceptor, leading to methane oxidation rates of 45–72 pmol cell−1 day−1. Despite the general assumption of methanotrophs preferring microaerobic conditions, methane oxidation was most efficient under high oxygen concentrations (>600 μM). Low (<30 μM) oxygen concentrations still supported methane oxidation, but no methane oxidation was observed with trace oxygen concentrations (<9 μM) or under anoxic conditions. Remarkably, the presence of nitrate stimulated methane oxidation rates under oxic conditions, raising the methane oxidation rates by 50% when compared to oxic incubations with ammonium. Under anoxic conditions, no net methane consumption was observed; however, methanotroph abundances were two to three times higher in incubations with nitrate and sulfate compared to anoxic incubations with ammonium as the nitrogen source. Metagenomic sequencing revealed the absence of a complete denitrification pathway in the dominant methanotroph Methylobacter, but the most abundant methylotroph Methylotenera seemed capable of denitrification, which can possibly play a role in the enhanced methane oxidation rates under nitrate-rich conditions.

An emended description of Arcobacter anaerophilus Sasi Jyothsna et al. 2013: genomic and phenotypic insights.

Arcobacter anaerophilus was originally described as the first obligate anaerobe in this genus by Sasi Jyothsna et al. 2013. The complete genome sequence of the type strain of this species was determined and analysed. Genes characteristic for organisms capable of aerobic growth were identified, and the ability of the organism to grow under microaerobic and aerobic conditions was confirmed in two independent laboratories. The description of A. anaerophilus is thus emended and the wider ramifications of these findings are discussed.

Bioconversion of Napier Grass Mixed with Soybean Curd Residue Producing Bioethanol through Simultaneous Saccharification and Fermentation in a Solid State Culture

Napier grass is a promising lignocellulosic biomass for bioethanol production because of its high cellulose content and high annual productivity. Converting a lignocellulosic biomass into a bioethanol usually takes two steps which resulted in a long processing time and sometimes includes the utilization of hazardous chemicals. Simultaneous saccharification and fermentation in a solid-state culture using single bioconversion agent, Neurospora sitophila Shear, can reduce the overall processing time and also increase the yield of the products. The research is aimed to determine the optimum aerobic and micro-aerobic conditions that yields the highest enzyme activity and bioethanol concentration from the mixture of Napier grass and soybean curd residue. The saccharification and fermentation process was conducted in the laboratory using an incubator at 33 o C. The cellulase enzyme activity was calculated as FPAse. The highest activity achieved was 0.538 filter paper unit with the optimum mass ratio of Napier grass to soybean curd residue was 1:1 on the second day of cultivation period. The fermentation process was conducted aerobically for two days and then followed by six days of micro-aerobic fermentation, resulting in the highest bioethanol yield of 2.12% (w/w) at the end of the culture period. The optimum mass ratio was found to be 9:1. This study shows that Napier grass and simultaneous saccharification and fermentation method has a great potential for cellulase and bioethanol production, but further improvement on the micro-aerobic system is needed to maximize the bioethanol yield.

Simultaneous nitrification, denitrification and phosphorus removal in a continuous-flow moving bed biofilm reactor alternating microaerobic and aerobic conditions

A continuous-flow moving bed biofilm reactor (IAMBBR) alternating microaerobic and aerobic conditions was used to remove carbon, nitrogen and phosphorus through simultaneous nitrification and denitrification coupled to phosphorus removal (SNDPR). The IAMBBR was operated under different dissolved oxygen (DO) ranges (0.2–2, 0.2–3 and 0.2–4 mg L−1) and feed C/N ratios (2.8, 3.6 and 4.2) at HRT of 1 day. At a DO range of 0.2–3 mg L−1 and feed C/N ratio of 3.6, the IAMBBR achieved simultaneous removal of dissolved organic carbon (DOC), total inorganic nitrogen (TIN) and P-PO43− with average efficiencies of 100%, 62% and 75%, respectively. Illumina sequencing revealed the coexistence of nitrifiers and P-accumulating denitrifiers (e.g. Hydrogenophaga) in the IAMBBR biofilm. Batch activity tests showed that phosphorus uptake did not occur under stable anaerobic or anoxic conditions, nor under aerobic conditions in absence of nitrate.