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In this study, we performed 16S rRNA amplicon sequencing analysis of scalp hair shaft from 109 volunteers, who were surveyed using a questionnaire about daily scalp hair care, and employed multiple statistical analyses to elucidate the factors that contribute to the formation of bacterial community structures on scalp hair shaft. Scalp hair microbiota were found to be specific for each individual. Their microbiota were clearly divided into two clusters. Genus level richness of Pseudomonas (Ps) and Cutibacterium (Cu) contributed to the clusters. The clusters around Pseudomonas and Cutibacterium were named Ps-type and Cu-type, respectively. The host gender influenced the bacterial cell numbers of the major genera that included Cutibacterium, Lawsonella, Moraxella, and Staphylococcus on scalp hair shaft. In addition to host intrinsic factors, extrinsic factors such as hair styling and colouring affected the bacterial cell numbers of the major genera. These factors and chemical treatments, such as bleaching and perming, also affected the Ps-type to Cu-type ratios. These results suggest that bacterial community structures on scalp hair shaft are influenced by both intrinsic and extrinsic factors.

There is a renewed interest in acetone-butanol-ethanol (ABE) fermentation from renewable substrates for the sustainable and environment-friendly production of biofuel and platform chemicals. However, the ABE fermentation is associated with several challenges due to the presence of heterogeneous components in the renewable substrates and the intrinsic characteristics of ABE fermentation process. Hence, there is a need to select optimal substrates and modify their characteristics suitable for the ABE fermentation process or microbial strain. This "designed biomass" can be used to establish the consolidated bioprocessing systems. As there are very few reports on designed biomass, the main objectives of this review are to summarize the main challenges associated with ABE fermentation from renewable substrates and to introduce feasible strategies for designing the substrates through pretreatment and hydrolysis technologies as well as through the establishment of consolidated bioprocessing systems. This review offers new insights on improving the efficiency of ABE fermentation from designed renewable substrates.

Bacterial communities on various parts of the human body are distinct. We were the first to report the existence of a stable bacterial community on human scalp hair and demonstrated that an analysis of its structure by terminal restriction fragment length polymorphism (T-RFLP) is helpful for individual discrimination. However, the ecology of the bacterial community on human scalp hair has not yet been elucidated in detail. We herein investigated the mode, quantity, and phylogeny of bacterial communities on the human hair shaft and root and showed the results obtained from one representative individual. Direct SEM observations of hair, without a pretreatment, confirmed the ubiquitous presence of bacteria-like coccoids and rods on the shaft and root of hair from the human scalp, with 105–106 cells cm−2 of hair and 107 cells cm−2 of hair, respectively. These values corresponded to the 16S rRNA gene copy numbers obtained by qPCR. These numbers were not significantly affected by detergent washing. These results represented those obtained from many individuals with different hair lengths, ages, and gender. The major OTUs on the human scalp hair shaft and root were the same and included two species of Pseudomonas (phylum Proteobacteria), Cutibacterium and Lawsonella (phylum Actinobacteria), and Staphylococcus (phylum Firmicutes). These results suggest that major bacteria on the human hair shaft are indigenous and derived from the hair root.

Despite efforts to address the composition of the microbial community during the anaerobic treatment of palm oil mill effluent (POME), its composition in relation to biodegradation in the full-scale treatment system has not yet been extensively examined. Therefore, a thorough analysis of bacterial and archaeal communities was performed in the present study using MiSeq sequencing at the different stages of the POME treatment, which comprised anaerobic as well as facultative anaerobic and aerobic processes, including the mixed raw effluent (MRE), mixing pond, holding tank, and final discharge phases. Based on the results obtained, the following biodegradation processes were suggested to occur at the different treatment stages: (1) Lactobacillaceae (35.9%) dominated the first stage, which contributed to high lactic acid production; (2) the higher population of Clostridiaceae in the mixing pond (47.7%) and Prevotellaceae in the holding tank (49.7%) promoted acetic acid production; (3) the aceticlastic methanogen Methanosaetaceae (0.6-0.8%) played a role in acetic acid degradation in the open digester and closed reactor for methane generation; (4) Syntrophomonas (21.5-29.2%) appeared to be involved in the degradation of fatty acids and acetic acid by syntrophic cooperation with the hydrogenotrophic methanogen, Methanobacteriaceae (0.6-1.3%); and (5) the phenols and alcohols detected in the early phases, but not in the final discharge phase, indicated the successful degradation of lignocellulosic materials. The present results contribute to a better understanding of the biodegradation mechanisms involved in the different stages of the full-scale treatment of POME.

Autothermal thermophilic aerobic digestion (ATAD) is used to treat human excreta hygienically. We previously reported a unique full-scale ATAD, showing distinctive bacterial community transitions and producing high-nitrogen-content liquid fertilizer; nevertheless, the mechanism remains unclear. One hypothesis involves using a gas-inducing (GI) agitator. We designed a lab-scale GI system and compared it with a disk-turbine (DT) agitator system by mimicking the temperature shift of full-scale ATAD. The agitation system and its agitation speed greatly affected physicochemical properties and bacterial community structure. GI system at 1000 rpm (GI1000; high total carbon removal efficiency, 88.3%), with few nitrifying and denitrifying bacteria, maintained a high ammoniacal nitrogen concentration and had more shared operational taxonomic units related to Acinetobacter sp., Arcobacter sp., and Longimicrobium sp. with the full-scale ATAD compared with the GI system at 490 rpm and DT system at 1000 rpm (DT1000). Furthermore, DT1000, with a high abundance of nitrifying and denitrifying bacteria such as Alcaligenes aquatilis and Pseudomonas caeni, removed 94.7% total nitrogen with 71.9% total carbon removal efficiency. These results suggested that shear stress and oxygen supply system would change the bacterial community structure, thus affected ATAD performances. Consequently, it is possible that ATAD can be applied for not only production of highly nitrogen-containing liquid fertilizer but also extremely nitrogen removal of wastewater.

This study aimed to evaluate greenhouse gas (GHG) emissions from conventional cultivation (S1) of seedless lime (SL) fruit in Hau Giang province, in the Mekong Delta region of Vietnam. We adjusted the scenarios by replacing 25% and 50% of nitrogen chemical fertilizer with respective amounts of N-based organic fertilizer (S2 and S3). Face-to-face interviews were conducted to collect primary data. Life cycle assessment (LCA) methodology with the “cradle to gate” approach was used to estimate GHG emission based on the functional unit of one hectare of growing area and one tonnage of fresh fruit weight. The emission factors of agrochemicals, fertilizers, electricity, fuel production, and internal combustion were collected from the MiLCA software, IPCC reports, and previous studies. The S1, S2, and S3 emissions were 7590, 6703, and 5884 kg-CO2 equivalent (CO2e) per hectare of the growing area and 273.6, 240.3, and 209.7 kg-CO2e for each tonnage of commercial fruit, respectively. Changing fertilizer-based practice from S1 to S2 and S3 mitigated 887.0–1706 kg-CO2e ha–1 (11.7–22.5%) and 33.3–63.9 kg-CO2e t–1 (12.2–25.6%), respectively. These results support a solution to reduce emissions by replacing chemical fertilizers with organic fertilizers.

In this study, we investigated and compared characteristics of the bacterial community structures on hair (scalp hair) and scalp in 18 individuals. Significant differences were found between the sites, in terms of cell density, alpha and beta diversity, and relative abundance of the phyla, Firmicutes and Proteobacteria, whereas no difference was found in relative abundance of the phylum Actinobacteria. Bacteria of the genus Cutibacterium showed similar relative abundance at both sites, whereas those of genus Pseudomonas were highly abundant on hair, and those of genus Staphylococcus were significantly lesser in abundance on hair than on scalp. Statistical correlations between the sites were high for the individual relative abundance of five major operational taxonomic units (OTUs). This suggests that the bacterial community structure on hair is composed of hair-specific genus, Pseudomonas, and skin-derived genera, Cutibacterium and Staphylococcus, and is distinguishable from other human skin microbiomes.

Biobutanol is well known as a suitable substitute for gasoline, which can be applied without engine modification. Butanol toxicity to the producer strain causes difficulties to grow strain of higher than 4 g/L dry cell weight and to produce butanol higher than 20 g/L. Fermentation using high initial cell density has been reported to enhance butanol productivity. In addition, oleyl alcohol has been recognized for effective extraction of butanol because of its selectivity and biocompatibility with reduced the effect of toxicity. Butanol fermentation with high cell density and large extractant volume has not been reported and is expected to improve butanol production in a minimum medium volume setting. Clostridium saccharoperbutylacetonicum N1-4, C. beijerinckii NCIMB 8052 (8052), and C. acetobutylicum ATCC 824 (824) were used in this study. Three kinds of media, TYA, TY, and TY-CaCO3, were used in this conventional extractive fermentation. Then, in situ extractive fermentation with Ve/Vb ratios at 0.1, 0.5, 1.0, and 10 were used. Total butanol concentration was defined as the broth-based total butanol, which is the total amount of butanol produced in broth and extractant per the volume of broth. TYA medium yielded the highest total butanol concentrations at N1-4 (12 g/L), 8052 (11 g/L), and 824 (15 g/L), and the highest partition coefficient (3.7) among the three media with similar Ve/Vb ratio at 0.5. N1-4 yielded the highest increment of total butanol production (22 g/L) in the extractive fermentation with high cell density. Low butanol concentration of 0.8 g/L in the broth was maintained using the extractant at a broth volume ratio (Ve/Vb) much lower than 4.4 g/L with a ratio of 0.5. Ve/Vb ratio of 10 which provided 2-fold higher total butanol concentration (28 g/L) than that of 11 g/L obtained using a Ve/Vb ratio of 0.5. These results indicated that a larger volume of extractant to broth improved total butanol concentration by reducing butanol toxicity and led to high medium based butanol yield in fermentation using high cell density. ©2020. CBIORE-IJRED. All rights reserved

Enterococcus mundtii QU25, a non-dairy lactic acid bacterium of the phylum Firmicutes, is capable of simultaneously fermenting cellobiose and xylose, and is described as a promising strain for the industrial production of optically pure l-lactic acid (≥ 99.9%) via homo-fermentation of lignocellulosic hydrolysates. Generally, Firmicutes bacteria show preferential consumption of sugar (usually glucose), termed carbon catabolite repression (CCR), while hampering the catabolism of other sugars. In our previous study, QU25 exhibited apparent CCR in a glucose-xylose mixture phenotypically, and transcriptional repression of the xylose operon encoding initial xylose metabolism genes, likely occurred in a CcpA-dependent manner. QU25 did not exhibit CCR phenotypically in a cellobiose-xylose mixture. The aim of the current study is to elucidate the transcriptional change associated with the simultaneous utilization of cellobiose and xylose. To this end, we performed RNA-seq analysis in the exponential growth phase of E. mundtii QU25 cells grown in glucose, cellobiose, and/or xylose as either sole or co-carbon sources. Our transcriptomic data showed that the xylose operon was weakly repressed in cells grown in a cellobiose-xylose mixture compared with that in cells grown in a glucose-xylose mixture. Furthermore, the gene expression of talC, the sole gene encoding transaldolase, is expected to be repressed by CcpA-mediated CCR. QU25 metabolized xylose without using transaldolase, which is necessary for homolactic fermentation from pentoses using the pentose-phosphate pathway. Hence, the metabolism of xylose in the presence of cellobiose by QU25 may have been due to 1) sufficient amounts of proteins encoded by the xylose operon genes for xylose metabolism despite of the slight repression of the operon, and 2) bypassing of the pentose-phosphate pathway without the TalC activity. Accordingly, we have determined the targets of genetic modification in QU25 to metabolize cellobiose, xylose and glucose simultaneously for application of the lactic fermentation from lignocellulosic hydrolysates.

Product inhibition by butanol and acetone is a known drawback in acetone-butanol-ethanol (ABE) fermentation. Extractive fermentation improves butanol production by several ABE-producing Clostridium spp., but only low volume ratios ( 24 h, it produced a higher concentration of total butanol (i.e., butanol produced in all the phases per broth volume used) of 24.2 g/L-broth after 96 h compared with 14.4 g/L-broth at a Ve/Vb ratio of 1, resulting in a low butanol concentration in the aqueous phase. The use of cells immobilized with calcium alginate beads shortened the lag phase to

A novel actinobacterial strain, designated C12CA1T, was isolated from forest soil in the conservation area of Chulabhorn dam, Thailand, and its taxonomic position was determined by using a polyphasic approach. Strain C12CA1T contained meso-2,6 diaminopimelic acid in the cell-wall peptidoglycan, and arabinose and galactose as diagnostic sugars of the whole-cell hydrolysate. On the basis of morphological and chemotaxonomic characteristics, strain C12CA1T was classified in the genus Amycolatopsis . It contained MK-9(H4) as the predominant menaquinone, C16 : 0, iso-C15 : 0 and iso-C16 : 0 as the major cellular fatty acids, and several phospholipids consisting of diphosphotidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, hydroxyphosphatidylethanolamine, phosphatidylinositol mannosides and an unidentified glucosamine-containing phospholipid. Based on 16S rRNA gene sequence and phylogenetic analyses, strain C12CA1T was closely related to Amycolatopsis vancoresmycina DSM 44592T (98.96 %) and Amycolatopsis pretoriensis JCM 12673T (98.82 %). The strain exhibited low DNA–DNA relatedness values with A. vancoresmycina DSM 44592T (6.9±0.2–11.6±1.9 %) and A. pretoriensis JCM 12673T (8.8±0.3–9.2±1.8 %). The DNA G+C content of strain C12CA1T was 69.8 mol%. Based on the results of polyphasic characterization, strain C12CA1T represents a novel species of the genus Amycolatopsis , for which the name Amycolatopsis silviterrae sp. nov. is proposed. The type strain is C12CA1T (=TBRC 1456T=NBRC 111116T).

The microbiological effects of palm oil mill effluent (POME) final discharge upon a receiving river were assessed in this study by using the nucleic acid double staining assay based on flow cytometry. The functional status of the bacterial community at the single-cell level was determined with regards to their abundance, viability and nucleic acid content to monitor the effects of POME final discharge on the affected river. The effluent resulted in the increment of the total cell concentration (TCC) and viable cells which were correlated with the increment of biological oxygen demand (BOD5) and total organic carbon (TOC) concentrations in the receiving river. The shift of low nucleic acid (LNA) to high nucleic acid (HNA) bacterial cells in the affected river suggested the transformation of dormant to active cells due to the POME final discharge. This is the first study to report on the shift of LNA/HNA ratios which may serves as a potential bioindicator in the screening of the anthropogenic effects due to POME final discharge in river water with originally high LNA proportions. Monitoring the effluent discharge at low trophic level using flow cytometry is a rapid and sensitive approach when compared to the current physicochemical assessment method. This approach allows for the screening of river water contamination caused by POME final discharge prior to a full assessment using the recently proposed specific bacterial indicators.

A thorough outlook on the effect of palm oil mill effluent (POME) final discharge towards bacterial community dynamics in the receiving river is provided in this study by using a high-throughput MiSeq. The shift of bacterial composition could be used to determine the potential bacterial indicators to indicate contamination caused by POME. This study showed that the POME final discharge did not only alter the natural physicochemical properties of the river water but also caused the reduction of bacterial diversity in the receiving river. The Chromatiaceae and Alcaligenaceae which were not detected in the upstream but were detected in the downstream part of the river are proposed as the indicator bacteria to indicate the river water contamination caused by POME final discharge. The emergence of either one or both bacteria in the downstream part of the river were shown to be carried over by the effluent. Therefore, an accurate pollution monitoring approach using bacterial indicator is expected to complement the conventional POME pollution assessment method which is currently dependent on the physicochemical properties of the final discharge. This is the first study that reported on the potential indicator bacteria for the assessment of river water contamination caused by POME final discharge.

Previously, a unique co-compost produced by composting empty fruit bunch with anaerobic sludge from palm oil mill effluent, which contributed to establishing a zero-emission industry in Malaysia. Little was known about the bacterial functions during the composting process and fertilization capacity of this co-compost. We isolated 100 strains from the co-compost on 7 types of enumeration media and screened 25 strains using in vitro tests for 12 traits, grouping them according to three functions: plant growth promoting (fixation of nitrogen; solubilization of phosphorus, potassium, and silicate; production of 3-indoleacetic acid, ammonia, and siderophore), biocontrolling (production of chitinase and anti-Ganoderma activity), and composting (degradation of lignin, xylan, and cellulose). Using 16S rRNA gene sequence analysis, 25 strains with strong or multi-functional traits were found belong to the genera Bacillus, Paenibacillus, Citrobacter, Enterobacter, and Kosakonia. Furthermore, several strains of Citrobacter sedlakii exhibited a plant growth-stimulation in vivo komatsuna plant cultivation test. In addition, we isolated several multifunctional strains; Bacillus tequilensis CE4 (biocontrolling and composting), Enterobacter cloacae subsp. dissolvens B3 (plant growth promoting and biocontrolling), and C. sedlakii CESi7 (plant growth promoting and composting). Some bacteria in the co-compost play significant roles during the composting process and plant cultivation after fertilization, and some multifunctional strains have potential for use in accelerating the biodegradation of lignocellulosic biomass, protecting against Ganoderma boninense infection, and increasing the yield of palm oil.

Decline in forest productivity due to forest conversion is defining the Bornean landscape. Responses of bacterial communities due to land-use changes are vital and could define our understanding of ecosystem functions. This study reports the changes in bacterial community structure in organic soil (0-5 cm; O-Horizon) and organic-mineral soil (5-15 cm; A-Horizon) across Maliau Basin Conservation Area old growth forest (MBOG), Fragment E logged forest (FELF) located in Kalabakan Forest Reserve to Benta Wawasan oil palm plantation (BWOP) using two-step PCR amplicon analysis of bacteria DNA on Illumina Miseq next generation sequencing. A total of 30 soil samples yielded 893,752-OTU reads at ≥97% similarity from 5,446,512 good quality sequences. Soil from BWOP plantation showed highest unshared OTUs for organic (49.2%) and organic-mineral (50.9%) soil. MBOG soil showed a drop in unshared OTUs between organic (48.6%) and organic-mineral (33.9%). At phylum level, Proteobacteria dominated MBOG but shifted to Actinobacteria in logged and plantation soil. Present findings also indicated that only FELF exhibited change in bacterial communities along the soil depth, moving from the organic to the organic-mineral layer. Both layers of BWOP plantation soils deviated from other forests' soil in β-diversity analysis. To our knowledge, this is the first report on transitions of bacterial community structures with different soil horizons in the tropical rainforest including Borneo, Sabah. Borneo tropical soils form a large reservoir for soil bacteria and future exploration is needed for fully understanding the diversity structure and their bacterial functional properties.

The use of probiotic bacteria to control bacterial infection in farmed fish is of clear practical interest. The aims of this study were to isolate and select a probiotic Bacillus sp. and to evaluate the effects of its supplementation on the growth and disease resistance of hybrid catfish. Bacillus siamensis strain B44v, selectively isolated from Thai pickled vegetables (Phak-dong), displayed a high potential as a probiotic in catfish culture. This bacterium produced a bacteriocin-like substance and exhibited a broad-spectrum antibacterial activity inhibiting both Gram-positive and Gram-negative bacteria, especially the fish pathogens Aeromonas hydrophila and Streptococcus agalactiae. The susceptibility to all 14 antibiotics tested implies its less possibility to be the antibiotic-resistant bacterium. Bacillus siamensis strain B44v possessed interesting adhesion properties, as shown by its high percentages of hydrophobicity (64.8%), auto-agglutination (73.8%), co-aggregation (67.2% with A. hydrophila FW52 and 63.5% with S. agalactiae F3S), and mucin binding (88.7%). The strain B44v survived simulated gastrointestinal conditions and produced protease and cellulase enzymes. Hybrid catfish (C. macrocephalus × C. gariepinus) were employed in the feed-trial experiments. Fish fed diet containing strain B44v (107 CFU/g feed) displayed not only no mortality but also growth improvement. At the end of the feed trial, fish were challenged by an intraperitoneal injection of Aeromonas hydrophila FW52. The Bacillus siamensis strain B44v fed fish survived (75.0%; p < 0.05) better than the controls (36.7%; p < 0.05) after a two week challenge. These collective results present for the first time the potential of Bacillus siamensis strain B44v for use as a bacterial probiotic in aquaculture.

Enterococcus faecium QU 50, a novel thermophilic L-lactic acid (LA) producing strain, was used in this study to ferment sugar mixtures into LA. Under the optimal fermentation conditions (50 °C, pH 6.5), strain QU 50 could ferment both mixed glucose/xylose sugars with relaxed CCR and mixed cellobiose/xylose sugars simultaneously without CCR to produce homo L-LA. The activity of enzymes related to xylose metabolism was also investigated. In the cells grown in a medium containing cellobiose/xylose, the activity of xylose isomerase and xylulose kinase, was 3.22 and 1.91 times higher, respectively, as compared to that of cells grown in a glucose/xylose medium. Strain QU 50 produced 70.8 g L−1 of L-LA with a yield of 1.04 g g−1 and a productivity of 2.95 g L−1 h−1 from simulated energy cane hydrolysate in batch fermentation. Immobilisation of strain QU 50 improved the operational stability of open repeated fermentation (three cycles), resulting in 61.1–64.3 g L−1 of L-LA with a yield of 1.01–1.02 g g−1 and a productivity of 3.22–3.82 g L−1 h−1. Thus, an efficient and cost-effective fermentation system was successfully established for L-LA production from sugar mixtures.

We previously reported the metabolic analysis of butanol and acetone production from exogenous acetate by (13)C tracer experiments (Gao et al., RSC Adv., 5, 8486-8495, 2015). To clarify the influence of acetate on acetone-butanol-ethanol (ABE) production, we first performed an enzyme assay in Clostridium saccharoperbutylacetonicum N1-4. Acetate addition was found to drastically increase the activities of key enzymes involved in the acetate uptake (phosphate acetyltransferase and CoA transferase), acetone formation (acetoacetate decarboxylase), and butanol formation (butanol dehydrogenase) pathways. Subsequently, supplementation of acetate during acidogenesis and early solventogenesis resulted in a significant increase in ABE production. To establish an efficient ABE production system using acetate as a co-substrate, several shot strategies were investigated in batch culture. Batch cultures with two substrate shots without pH control produced 14.20 g/L butanol and 23.27 g/L ABE with a maximum specific butanol production rate of 0.26 g/(g h). Furthermore, pH-controlled (at pH 5.5) batch cultures with two substrate shots resulted in not only improved acetate consumption but also a further increase in ABE production. Finally, we obtained 15.13 g/L butanol and 24.37 g/L ABE at the high specific butanol production rate of 0.34 g/(g h) using pH-stat co-feeding method. Thus, in this study, we established a high ABE production system using glucose and acetate as co-substrates in a pH-stat co-feeding system with C. saccharoperbutylacetonicum N1-4.

A unique method to produce highly optically-active l-lactic acid and soil amendments that promote plant growth from food waste was proposed. Three Bacillus strains Bacillus subtilis KBKU21, B. subtilis N3-9 and Bacillus coagulans T27, were used. Strain KBKU21 accumulated 36.9 g/L l-lactic acid with 95.7% optical activity and 98.2% l-lactic acid selectivity when fermented at 43°C for 84 h in a model kitchen refuse (MKR) medium. Residual precipitate fraction (anaerobically-fermented MKR (AFM) compost) analysis revealed 4.60%, 0.70% and 0.75% of nitrogen (as N), phosphorous (as P2O5), and potassium (as K2O), respectively. Additionally, the carbon to nitrogen ratio decreased from 13.3 to 10.6. AFM compost with KBKU21 promoted plant growth parameters, including leaf length, plant height and fresh weight of Brassica rapa (Komatsuna), than that by chemical fertilizers or commercial compost. The concept provides an incentive for the complete recycling of food waste, contributing towards a sustainable production system.

This study implemented the pyrosequencing technique and real-time quantitative PCR to determine the prevalence of foodborne pathogenic bacteria (FPB) and as well as the ecological correlations of background biota and FPB present on restaurant cutting boards (CBs) collected in Seri Kembangan, Malaysia. The prevalence of FPB in high background biota (HBB) was lower (0.24%) compared to that of low background biota (LBB) (0.54%). In addition, a multiple linear regression analysis indicated that only HBB had a significant ecological correlation with FPB. Furthermore, statistical analysis revealed that the combinations of Clostridiales, Flavobacteriales, and Lactobacillales orders in HBB had significant negative associations with FPB, suggesting that these bacteria may interact to ensure survivability and impair the growth of pathogenic bacteria.

A few strains of lactic acid bacteria metabolise xylose into optically pure L-lactic acid (LA). This study achieved an effective homofermentative cell recycle continuous fermentation of xylose to L-LA with high concentration, productivity, and yield using Enterococcus mundtii QU 25. In conventional continuous fermentation, the optimal xylose concentration in the feeding solution is 50 g L−1, and the optimal dilution rate is 0.15 h−1. Continuous fermentation with cell recycling using a microfiltration membrane module produced an L-LA concentration of 32.3 g L−1 with a yield of 0.789 g g−1 and a productivity of 5.33 g L−1 h−1. Controlling pH and optimising the feeding medium were important for achieving a high L-LA yield with strain QU 25. Using corn steep liquor-containing medium at pH 6.2, a maximum L-LA concentration, yield and productivity were achieved at 41.0 g L−1, 1.01 g g−1, and 6.15 g L−1 h−1, respectively. This study is the first to report on continuous fermentation with cell recycling for lactic acid production from xylose.

A unique autothermal thermophilic aerobic digestion (ATAD) process has been used to convert human excreta to liquid fertilizer in Japan. This study investigated the changes in physicochemical and bacterial community characteristics during the full-scale ATAD process operated for approximately 3 weeks in 2 different years. After initiating simultaneous aeration and mixing using an air-inducing circulator (aerator), the temperature autothermally increased rapidly in the first 1 to 2 days with exhaustive oxygen consumption, leading to a drastic decrease and gradual increase in oxidation-reduction potential in the first 2 days, reached >50°C in the middle 4 to 6 days, and remained steady in the final phase. Volatile fatty acids were rapidly consumed and diminished in the first 2 days, whereas the ammonia nitrogen concentration was relatively stable during the process, despite a gradual pH increase to 9.3. Principal-coordinate analysis of 16S rRNA gene amplicons using next-generation sequencing divided the bacterial community structures into distinct clusters corresponding to three phases, and they were similar in the final phase in both years despite different transitions in the middle phase. The predominant phyla (closest species, dominancy) in the initial, middle, and final phases were Proteobacteria ( Arcobacter trophiarum , 19 to 43%; Acinetobacter towneri , 6.3 to 30%), Bacteroidetes ( Moheibacter sediminis , 43 to 54%), and Firmicutes ( Thermaerobacter composti , 11 to 28%; Heliorestis baculata , 2.1 to 16%), respectively. Two predominant operational taxonomic units (OTUs) in the final phase showed very low similarities to the closest species, indicating that the process is unique compared with previously published ones. This unique process with three distinctive phases would be caused by the aerator with complete aeration. IMPORTANCE Although the autothermal thermophilic aerobic digestion (ATAD) process has several advantages, such as a high degradation capacity, a short treatment period, and inactivation of pathogens, one of the factors limiting its broad application is the high electric power consumption for aerators with a full-scale bioreactor. We elucidated the dynamics of the bacterial community structures, as well as the physicochemical characteristics, in the ATAD process with a full-scale bioreactor from human excreta for 3 weeks. Our results indicated that this unique process can be divided into three distinguishable phases by an aerator with complete aeration and showed a possibility of shortening the digestion period to approximately 10 days. This research not only helps to identify which bacteria play significant roles and how the process can be improved and controlled but also demonstrates an efficient ATAD process with less electric power consumption for worldwide application.

The economic feasibility of acetone–butanol–ethanol (ABE) fermentation is greatly affected by the type of raw material used. The easy availability of eucalyptus from marginal environments is an alternative feedstock for use as raw material to reduce the production cost. In this study, hydrolyzed eucalyptus was used for ABE production without any nutrients supplementation. Increasing the solid concentration in the eucalyptus slurry from 6.7% (w-dry matter/v) to 25% led to an increase in the initial glucose concentration from 33.7 g/L to 86.7 g/L after enzymatic hydrolysis. Dosed cellulases not only hydrolyzed cellulose but also supplied nitrogen source for ABE producing strain. However, ABE production from the obtained hydrolysate decreased when the solid concentration was increased to more than 10%. The maximum ABE of 12.3 g/L was obtained at 10% solid concentration, with an initial glucose concentration of approximately 40 g/L. In addition, the fermentation capability of eucalyptus hydrolysate was found to be improved by diluting the hydrolysate, which prevented inhibition by substrate and fermentation inhibitors. Finally, ABE concentration was improved to 13.1 g/L by diluting the hydrolysate from the initial solid concentration of 25% to an initial glucose concentration of 45 g/L, which resulted in ABE productivity of 0.109 g/L/h and ABE yield of 0.413 g/g. Thus, the high ABE production from eucalyptus makes it a potential feedstock for biofuel production.

The development and implementation of renewable materials for the production of versatile chemical resources have gained considerable attention recently, as this offers an alternative to the environmental problems caused by the petroleum industry and the limited supply of fossil resources. Therefore, the concept of utilizing biomass or wastes from agricultural and industrial residues to produce useful chemical products has been widely accepted. Lactic acid plays an important role due to its versatile application in the food, medical, and cosmetics industries and as a potential raw material for the manufacture of biodegradable plastics. Currently, the fermentative production of optically pure lactic acid has increased because of the prospects of environmental friendliness and cost-effectiveness. In order to produce lactic acid with high yield and optical purity, many studies focus on wild microorganisms and metabolically engineered strains. This article reviews the most recent advances in the biotechnological production of lactic acid mainly by lactic acid bacteria, and discusses the feasibility and potential of various processes.

During acetone–butanol–ethanol (ABE) fermentation by clostridia, acetate is reutilised for butanol production. In this study, we investigated the characteristics of ABE production from acetate and analysed the metabolism of exogenously added acetate by Clostridium saccharoperbutylacetonicum N1-4. Supplementation of 4 g L−1 exogenous acetate, to media containing glucose, increased not only concentrations of butanol (48.3%) and acetone (90.5%), but also the ratio of acetone to butanol (27.1%), which suggested that acetate addition altered the metabolic flux. Acetate could not be metabolised in the absence of glucose, thus glycolysis appeared to be necessary for acetate utilisation. In order to clarify the metabolism of exogenous acetate, 13C tracer experiments were performed by supplementing [1,2-13C2] acetate in a culture broth. Based on the results of gas chromatography-mass spectroscopy analysis, we first confirmed both butanol and acetone formation from acetate. Further, the acetate-to-butanol efficiency will significantly decrease when more acetate than 2–4 g L−1 is added to the fermentation, while acetate-to-acetone efficiency may remain high (up to a ratio of 2 mol acetate per 1 mol glucose fed). Moreover, the culture supplemented with acetate exhibited an increase in conversion efficiency of glucose to butanol and acetone, from 0.196% to 19.5% and from 0 to 7.64%, respectively, even during acidogenesis. Thus, we first revealed quantitatively that acetate addition induced solvent production during the early growth phase, and increased metabolic flux to acetone and butanol production from both acetate and glucose.

Butanol has recently attracted attention as an alternative biofuel because of its various advantages over other biofuels. Many researchers have focused on butanol fermentation with renewable and sustainable resources, especially lignocellulosic materials, which has provided significant progress in butanol fermentation. However, there are still some drawbacks in butanol fermentation in terms of low butanol concentration and productivity, high cost of feedstock and product inhibition, which makes butanol fermentation less competitive than the production of other biofuels. These hurdles are being resolved in several ways. Genetic engineering is now available for improving butanol yield and butanol ratio through overexpression, knock out/down, and insertion of genes encoding key enzymes in the metabolic pathway of butanol fermentation. In addition, there are also many strategies to improve fermentation technology, such as multi-stage continuous fermentation, continuous fermentation integrated with immobilization and cell recycling, and the inclusion of additional organic acids or electron carriers to change metabolic flux. This review focuses on the most recent advances in butanol fermentation especially from the perspectives of genetic engineering and fermentation technology.

Autothermal thermophilic aerobic digestion (ATAD) is conducted for stabilization of sludge waste and is driven by the action of various microorganisms under aerobic conditions. However, the mechanism controlling bacterial community changes during ATAD via three (initial, middle and final) phases is currently unclear. To investigate this mechanism, activity analysis and a microcosm assay with shaking were performed on a bacterial community during the initial, middle, and final phases of incubation. Cell lysis activities toward gram-negative bacteria, but not gram-positive bacteria, were detected in the ATAD samples in the middle and final phases. During shaking incubation in initial-phase samples at 30 °C, major operational taxonomic units (OTUs) related to Acinetobacter indicus and Arcobacter cibarius dramatically increased along with decreases in several major OTUs. In middle-phase samples at 45 °C, we observed a major alteration of OTUs related to Caldicellulosiruptor bescii and Aciditerrimonas ferrireducens, together with distinct decreases in several other OTUs. Final-phase samples maintained a stable bacterial community with major OTUs showing limited similarities to Heliorestis baculata, Caldicellulosiruptor bescii, and Ornatilinea apprima. In conclusion, the changes in the bacterial community observed during ATAD could be partially attributed to the cell lysis activity toward gram-negative bacteria in the middle and final phases. The microcosm assay suggested that certain physical factors, such as a high oxygen supply and shearing forces, also might contribute to bacterial community changes in the initial and middle phases, and to the stable bacterial community in the final phase of ATAD.

A unique compost called Satsuma soil is produced from sewage sludge by a hyperthermal composting process in Kagoshima City, Japan. The composting process is carried out at a controlled temperature of at least 80°C and the resulting compost might be useful for recycling sustainable agricultural products. The extremely thermophilic bacterial genus Calditerricola was initially isolated from the high-temperature compost. Likewise, the bacteria were previously isolated from material sludge. It is believed that bacteria in this genus might be involved in the hyperthermal composting process. Calditerricola bacteria are distributed not only in compost, but also in all of its material sludge, and are more abundant in material sludge than in compost. Moreover, based on investigations of samples near geothermal areas in high temperature conditions, such as volcanoes, Calditerricola was presumed to originate in the volcanic ash of Mt. Sakurajima in Kagoshima City, Japan. However, its precise origin and ecology are unclear. Thus, in this study, a new molecular biological method called enrichment most probable number (MPN)-PCR (eMPN-PCR) was established and used to quantitatively investigate the population and distribution of the extreme thermophile Calditerricola in environmental samples using genus-specific PCR primers. The eMPN-PCR method was an effective quantitative detection method with high sensitivity, yielding MPN estimates that were highly correlated with colony forming unit (CFU) estimates but a low detection threshold value.

A novel Gram-staining-positive, endospore-forming, rod-shaped, facultatively anaerobic, thermotolerant bacterium, designated strain MO-04T, was isolated from a marine animal resources (MAR) compost. The 16S rRNA gene sequence of strain MO-04T showed 99.4 % similarity with Bacillus thermolactis R-6488T, 94.1 % similarity with Bacillus thermoamylovorans CNCM I-1378T, 93.3 % similarity with Bacillus humi LMG 22167T, 93.2 % similarity with Bacillus niacini IFO 15566T and the similarities with other species were less than 93 %. DNA–DNA relatedness between strain MO-04T and B. thermolactis DSM 23332T was 45 %. The DNA G+C content of strain MO-04T was 33.4 mol%, comparatively lower than that of B. thermolactis R-6488T (35.0 mol%). Strain MO-04T grew at 35–61 °C (optimum 50 °C), pH 4.5–9.0 (optimum pH 7.2) and tolerated up to 8.0 % (w/v) NaCl (optimum 2 %). The MO-04T cell wall peptidoglycan type was meso-2,6-diaminopimelic acid, and the major fatty acids were C16 : 1, C14 : 1, C17 : 0 and C17 : 1. The major polar lipids were represented by diphosphatidylglycerol and phosphatidylglycerol and two unidentified phospholipids. The analysed polyphasic data presented here clearly indicate that the isolate MO-04T is considered to represent a novel species within the genus Bacillus for which the name Bacillus kokeshiiformis sp. nov. is proposed. The type strain of B. kokeshiiformis is MO-04T ( = JCM 19325T = KCTC 33163T).

By applying non-sterile open fermentation of food waste, various thermotolerant l -lactic acid-producing bacteria were isolated and identified. The predominant bacterial isolates showing higher accumulation of l -lactic acid belong to 3 groups of Bacillus coagulans , according to their 16S rRNA gene sequence similarities. B. coagulans strains M21 and M36 produced high amounts of l -lactic acid of high optical purity and lactic acid selectivity in model kitchen refuse medium and glucose–yeast extract–peptone medium. Other thermotolerant isolates resembling to Bacillus humi , B. ruris , B. subtilis , B. niacini and B. soli were also identified. These bacteria produced low amounts of l -lactic acid of more than 99% optical purity. All isolated strains showed the highest growth rate at temperatures around 55–60°C. They showed unique responses to various oxygen supply conditions. The majority of isolates produced l -lactic acid at a low overall oxygen transfer coefficient ( K L a ); however, acetic acid was produced instead of l -lactic acid at a high K L a . B . coagulans M21 was the only strain that produced high, consistent, and reproducible amounts of optically pure l -lactic acid (>99% optical purity) under high and low K L a conditions in a homo-fermentative manner.

The use of lignocellulosic biomass for the production of optically pure lactic acid remains challenging because it requires efficient utilisation of mixed sugars without carbon catabolite repression (CCR). Enterococcus mundtii QU 25, a novel L-lactic acid-producing strain, was used in this study to ferment mixed sugars. This strain exhibited apparent CCR in a glucose–xylose mixture; however, replacement of glucose by cellobiose (cellobiose–xylose mixture) led to simultaneous consumption of both sugars without CCR. The production of lactic acid and activity of enzymes related to xylose metabolism were also investigated. Xylose isomerase and xylulokinase specific activity in cellobiose–xylose grown cells was three times higher than that in glucose–xylose grown cells. The addition of yeast extract and ammonium hydroxide effectively improved sugar utilisation and cell growth. Under the optimal conditions with simulated lignocellulosic hydrolysates, a high L-lactic acid concentration (up to 163 g L−1) was produced with a yield of 0.870 g g−1 and maximum productivity of 7.21 g L−1 h−1 without CCR in the fed-batch fermentation. Thus, we could establish rapid and simultaneous consumption of hexose and pentose sugars by using a lactic acid bacterium strain, which significantly increased production of high-purity L-lactic acid.

Factors including the composition and concentration of mixed sugars, dilution rate, and cell density were examined to establish a highly efficient continuous acetone–butanol–ethanol (ABE) fermentation process using Clostridium saccharoperbutylacetonicum N1-4. During conventional continuous fermentation at a dilution rate of 0.15 h−1, the glucose/xylose mixture exhibited carbon catabolite repression (CCR) with an intensity (I CCR) of 4.18 and ABE productivity of 0.574 g L−1 h−1, while CCR was alleviated using a cellobiose/xylose mixture with 1.60 and 1.09 g L−1 h−1, respectively. Continuous fermentation with high cell density by cell recycling improved ABE productivity to 5.32 g L−1 h−1 at a dilution rate of 0.686 h−1 owing to high xylose consumption. Further optimization of mixed sugar concentration in the feeding medium induced the best performance of continuous ABE production from mixed sugar without CCR, relative to previous studies: ABE productivity, 6.09 g L−1 h−1; ABE yield, 0.214 g g−1; I CCR, 1.48.

Acetone-butanol-ethanol (ABE) fermentation using Clostridium saccharoperbutylacetonicum N1-4 and mixed sugars containing cellobiose and xylose was studied to establish efficient butanol production process without carbon catabolite repression (CCR). Although batch culture with glucose and xylose exhibited apparent CCR, we achieved simultaneous consumption of cellobiose and xylose. Moreover, preculture of the N1-4 strain with xylose yielded maximum butanol and solvent concentrations (16 and 23 g/L, respectively). Thus, we succeeded in ABE fermentation with mixed sugars of hexose and pentose, without CCR, by using wild-type ABE-producing clostridia. We also investigated the effect of various ratios of cellobiose and xylose on the fermentation process and yield. Increasing initial xylose concentration improved butanol and solvent concentrations and maximum xylose consumption rate. Fed-batch culture with cellobiose and xylose showed rapid and simultaneous sugar consumption and improved maximum consumption rate of both sugars.

Presently, several researchers are increasingly focusing on producing butanol as the next-generation fuel by acetone-butanol-ethanol (ABE) fermentation. Butanol has many superior characteristics compared to other biofuels, such as ethanol. However, its production by ABE fermentation faces the challenges of low productivity and yield because of product inhibition and heterofermentation, respectively, and thereby, high costs. Until date, molecular biological techniques and fermentation engineering methods have been applied for high butanol production. Although glucose remains the substrate of choice since traditional research, it is now necessary to substitute glucose derived from edible starch to other substrates from low-cost feedstock, such as agricultural residue. In addition, ABE-producing clostridia cannot directly produce butanol from lignocelluloses. Therefore, recent research is focusing on pretreatment and enzymatic saccharification of the complex molecules derived from agricultural residue for use as feedstock in butanol production. This article reviews traditional research, including the metabolism patterns and characteristics of ABE-producing clostridia. Furthermore, this article describes developments in ABE fermentation with respect to the establishment of highly efficient butanol production processes, such as batch, fed-batch, and continuous cultures, with the introduction of butanol removal, as well as butanol production from lignocellulosic biomasses or alternative substrates to sugars.

A recently developed rapid co-composting of oil palm empty fruit bunch (OPEFB) and palm oil mill effluent (POME) anaerobic sludge is beginning to attract attention from the palm oil industry in managing the disposal of these wastes. However, a deeper understanding of microbial diversity is required for the sustainable practice of the co-compositing process. In this study, an in-depth assessment of bacterial community succession at different stages of the pilot scale co-composting of OPEFB-POME anaerobic sludge was performed using 454-pyrosequencing, which was then correlated with the changes of physicochemical properties including temperature, oxygen level and moisture content. Approximately 58,122 of 16S rRNA gene amplicons with more than 500 operational taxonomy units (OTUs) were obtained. Alpha diversity and principal component analysis (PCoA) indicated that bacterial diversity and distributions were most influenced by the physicochemical properties of the co-composting stages, which showed remarkable shifts of dominant species throughout the process. Species related to Devosia yakushimensis and Desemzia incerta are shown to emerge as dominant bacteria in the thermophilic stage, while Planococcus rifietoensis correlated best with the later stage of co-composting. This study proved the bacterial community shifts in the co-composting stages corresponded with the changes of the physicochemical properties, and may, therefore, be useful in monitoring the progress of co-composting and compost maturity.