Detection of risk areas in dairy powder processes: The development of thermophilic spore forming bacteria taking into account their growth limits

Anoxybacillus flavithermus, Geobacillus stearothermophilus and Bacillus licheniformis are the main contaminants found in dairy powders. These spore-forming thermophilic bacteria, rarely detected in raw milk, persist, and grow during the milk powder manufacturing process. Moreover, in the form of spores, these species resist and concentrate in the powders during the processes. The aim of this study was to determine the stages of the dairy powder manufacturing processes that are favorable to the growth of such contaminants. A total of 5 strains were selected for each species as a natural contaminant of dairy pipelines in order to determine the minimum and maximum growth enabling values for temperature, pH, and aw and their optimum growth rates in milk. These growth limits were combined with the environmental conditions of temperature, pH and aw encountered at each step of the manufacture of whole milk, skim milk and milk protein concentrate powders to estimate growth capacities using cardinal models and the Gamma concept. These simulations were used to theoretically calculate the population sizes reached for the different strains studied at each stage in between two successive cleaning in place procedures. This approach highlights the stages at which risk occurs for the development of spore-forming thermophilic bacterial species. During the first stages of production, i.e. pre-treatment, pasteurization, standardization and pre-heating before concentration, physico-chemical conditions encountered are suitable for the development and growth of A. flavithermus, G. stearothermophilus and B. licheniformis. During the pre-heating stage and during the first effects in the evaporators, the temperature conditions appear to be the most favorable for the growth of G. stearothermophilus. The temperatures in the evaporator during the last evaporator effects are favorable for the growth of B. licheniformis. In the evaporation stage, low water activity severely limits the development of A. flavithermus.

Effects of thermophilic bacteria inoculation on maturity, gaseous emission and bacterial community succession in hyperthermophilic composting

Hyperthermophilic composting, characterized by temperatures equal to or exceeding 75 °C, offers superior compost maturity and performance. Inoculation with thermophilic bacteria presents a viable approach to achieving hyperthermophilic composting. This study investigates the effects of inoculating thermophilic bacteria, isolated at different temperatures (50 °C, 60 °C, and 70 °C) into compost on maturity, gaseous emissions, and microbial community dynamics during co-composting. Results indicate that the thermophilic bacteria inoculation treatments exhibited peak temperature on Day 3, with the maximum temperature of 75 °C reached two days earlier than the control treatment. Furthermore, these treatments demonstrated increased bacterial richness and diversity, along with elevated relative abundances of Firmicutes and Proteobacteria. They also fostered mutualistic correlations among microbial species, enhancing network connectivity and complexity, thereby facilitating lignocellulose degradation. Specifically, inoculation with thermophilic bacteria at 60 °C increased the relative abundance of Thermobifida and unclassified-f-Thermomonosporaceae (Actinobacteriota), whereas Bacillus, a thermophilic bacterium, was enriched in the 70 °C inoculation treatment. Consequently, the thermophilic bacteria at 60 °C and 70 °C enhanced maturity by 36 %-50 % and reduced NH3 emissions by 1.08 %-27.50 % through the proliferation of thermophilic heterotrophic ammonia-oxidizing bacteria (Corynebacterium). Moreover, all inoculation treatments decreased CH4 emissions by 6 %-27 % through the enrichment of methanotrophic bacteria (Methylococcaceae) and reduced H2S, Me2S, and Me2SS emissions by 1 %-25 %, 47 %-63 %, and 15 %-53 %, respectively. However, the inoculation treatments led to increased N2O emissions through enhanced denitrification, as evidenced by the enrichment of Truepera and Pusillimonas. Overall, thermophilic bacteria inoculation promoted bacteria associated with compost maturity while attenuating the relationship between core bacteria and gaseous emissions during composting.

Revealing the degrading-possibility of methyl red by two azoreductases of Anoxybacillus sp. PDR2 based on molecular docking

Azo dyes, as the most widely used synthetic dyes, are considered to be one of the culprits of water resources and environmental pollution. Anoxybacillus sp. PDR2 is a thermophilic bacterium with the ability to degrade azo dyes, whose genome contains two genes encoding azoreductases (named AzoPDR2-1 and AzoPDR2-2). In this study, through response surface methodology (RSM), when the initial pH, inoculation volume and Mg2+ addition amount were 7.18, 10.72% and 0.1 g/L respectively, the decolorization rate of methyl red (MR) (200 mg/L) could reach its maximum (98.8%). The metabolites after biodegradation were detected by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and liquid chromatography mass spectrometry (LC-MS/MS), indicating that MR was successfully decomposed into 4-aminobenzoic acid and other small substrates. In homologous modeling, it was found that both azoreductases were flavin-dependent azoreductases, and belonged to the α/β structure, using the Rossmann fold. In their docking results with the cofactor flavin mononucleotide (FMN), FMN bound to the surface of the protein dimer. Nicotinamide adenine dinucleotide (NADH) was superimposed on the plane of the pyrazine ring between FMN and the activity pocket of protein. Besides, both azoreductase complexes (azoreductase-FMN-NADH) exhibited a substrate preference for MR. Asn104 and Tyr74 played an important role in the combination of the azoreductase AzoPDR2-1 complex and the azoreductase AzoPDR2-2 complex with MR, respectively. This provided assistance for studying the mechanism of azoreductase biodegradation of azo dyes in thermophilic bacteria.

Compound mutation by ultraviolet and diethyl sulfate of protease producing thermophilic bacteria to hydrolyze excess sludge

Excess sludge (ES), a resource-rich organic waste, can be solubilized by thermophilic enzymes to extract proteins for sludge reduction and resources recovery. To solve the problems of low hydrolysis effect of ES and low enzyme producing ability of wild thermophilic bacteria, ultraviolet and diethyl sulfate (UV-DES) were adopted to mutate thermophilic bacteria in this study. Mutation sites were detected and annotated by whole genome sequencing analysis. The results showed that UV-DES mutagenesis could effectively improve enzyme-producing capacity of thermophilic bacteria and promote the hydrolysis of ES. The protease activity of the mutant strain KT16 was 46.7 % higher than that of the original strain DC8. The protein extraction rate with enzyme produced by KT16 reached 83.3 %. The total content of proteins recycled through KT16 enzyme solution was 3539.6 mg·L-1, 18.4 % higher than that of DC8. This work provided a theoretical idea and technical guidance for the protein recovery from ES.

Dataset describing the influence of culture conditions on the bioreduction of organic acids to alcohols by Thermoanaerobacter pseudethanolicus

The dataset describes the influence of culture conditions on the bioreduction of organic acids by Thermoanaerobacter pseudethanolicus as reported in [1]. The data shows that during glucose fermentation of Thermoanaerobacter pseudethanolicus the reducing equivalents are not only converted to ethanol and hydrogen but also, in the presence of carboxylic acids (C2-C6), to its corresponding alcohol. To maximize the alcohol production produced from their carboxylic acid, several experiments were performed to investigate the effect of various environmental factors (initial glucose concentration, pH, liquid-gas phase ratio, and inhibitory effects of alcohols) on growth. A kinetic experiment of glucose in the absence and presence of selected fatty acids are also presented as are data on selected enzyme activities related to alcohols and aldehydes and a time course study of the reduction of 13C1 labeled butyrate using glucose as a carbon source.

Analysis of glycosylated cardiolipins from thermophilic bacteria using GC-MS and LC-ESI-MS/MS methods

Unusual glucose-substituted cardiolipins (Glcx-CLs) in three genera of thermophilic bacteria, having more than one glycosidically linked glucose to the hydroxyl of the central glycerol of Glcx-CLs were identified for the first time in thermophilic bacteria of the genera Geobacillus, Meiothermus, and Thermus. The number of glucoses reached up to five units. The structure of glycosidically linked oligosaccharides was determined based on shotgun analysis MS (electrospray high-resolution tandem mass spectrometry), partially methylated alditol acetates were identified by GC-MS, both electron ionization (EI) and positive chemical ionization (PCI), hydrophilic interaction liquid chromatography (HILIC) separation and identification of CLs glycosides by high resolution MS-ESI, and digestion by specific glycosidases.

Off-line two-dimensional LC-tandem MS of menaquinones from thermophilic bacteria

Thermophilic bacteria of four genera in contrast to the commonly used production strains such as Bacillus subtilis, produce homologs other than menaquinone (MK) with seven isoprene units. The number of isoprene units and the configuration of double bonds are essential factors for their biological activity. The goal was to obtain a strain of bacteria that produces a wide range of MK homologs and only all-trans geometrical isomers, which was the strain G. kaustophilus. Using off-line two-dimensional LC-tandem MS in columns with the RP18 phase and the COSMOSIL cholester phase (separation according to the geometric configuration of double bonds) it was shown that thermophilic bacteria grown at different temperatures produce only all-trans isomers of menaquinones from MK-5 (menaquinone with five isoprenyl units) to MK-15 (fifteen isoprenyl units). Therefore, G. kaustophilus appears to be a biotechnologically important strain produces only trans isomers and additionally homologs from 5 to 15 isoprene units.

Analysis of phenotypic changes in high temperature and low pH extreme conditions of Alicyclobacillus sendaiensis PA2 related with the cell wall and sporulation genes

The A. sendaiensis PA2 is a polyextremophile bacterium. In this study, we analyze the A. sendaiensis PA2 genome. The genome was assembled and annotated. The A. sendaiensis PA2 genome structure consists of a 2,956,928 bp long chromosome and 62.77% of G + C content. 3056 CDSs were predicted, and 2921 genes were assigned to a putative function. The ANIm and ANIb value resulted in 97.17% and 96.65%, the DDH value was 75.5%, and the value of TETRA (Z-score) was 0.98. Comparative genomic analyses indicated that three systems are enriched in A. sendaiensis PA2. This strain has phenotypic changes in cell wall during batch culture at 65 °C, pH 5.0 and without carbon and nitrogen source. The presence of unique genes of cell wall and sporulation subsystem could be related to the adaptation of A. sendaiensis PA2 to hostile conditions.

Structure and function of extreme TLS DNA polymerase TTEDbh from Thermoanaerobacter tengcongensis

Translesion synthesis (TLS) is a kind of DNA repair that maintains the stability of the genome and ensures the normal growth of life in cells under emergencies. Y-family DNA polymerases, as a kind of error-prone DNA polymerase, mainly perform TLS. Previous studies have suggested that the occurrence of tumors is associated with the overexpression of human DNA polymerase of the Y family. And the combination of Y-family DNA polymerase inhibitors is promising for cancer therapy. Here we report the functional and structural characterization of a member of the Y-family DNA polymerases, TTEDbh. We determine TTEDbh is an extreme TLS polymerase that can cross oxidative damage sites, and further identify the amino acids and novel structures that are critical for DNA binding, synthesis, fidelity, and oxidative damage bypass. Moreover, previously unnoticed structural elements with important functions have been discovered and analyzed. These studies provide a more experimental basis for further elucidating the molecular mechanisms of DNA polymerase in the Y family. It could also shed light on the design of drugs to target tumors.

Exploring the humification process of municipal sludge in hyperthermophilic composting through metagenomic and untargeted metabolomic

Hyperthermophilic composting (HC) has been widely recognized for the advantage of high treatment efficiency for organic wastes. However, the humification process is still unclear. In this study, the humification process of HC was investigated, compared to conventional composting (CK). The results showed that the highest composting temperature, organic matter degradation rate, and humification index in HC were 92.62 °C, 23.98%, and 1.59, while those in CK were 70.23 °C, 14.49 %, and 1.04, indicating HC accelerated humification process. Moreover, the results of metagenomic and untargeted metabolomic showed that the genes and metabolisms related to carbohydrate, lipid, amino acid, fatty acid, and nucleotide were more abundant in HC. Consequently, the metabolic pathways regarding organic matter degradation and microbial reproduction were enhanced in the high temperature stage of HC, further accelerating the humification reaction in the low temperature stage. This work contributes to the comprehension of the humification mechanism in HC.

Effect of inoculating thermophilic bacterial consortia on compost efficiency and quality

The objective of this study was to investigate the potential effects of thermophilic bacterial consortia on compost efficiency and quality. The application of bacterial consortia resulted in an earlier onset of the thermophilic period (THP), an increased upper temperature limit, and an extended duration of the THP by 3-5 days compared to the control group (CK). Microbial inoculation significantly improved the efficiency of organic matter degradation, as well as the content of water-soluble nitrogen (WSN) and humic acid-carbon (HAC). In the case of consortium Ⅱ inoculation (T2), the activities of cellobiohydrolase, β-glucosidase, and protease were increased by 81.81 %, 70.13 %, and 74.09 % at the THP respectively compared to CK. During the maturation stage, T2 also exhibited the highest PV, n/PIII, n value (1.33) and HAC content (39.53 mg·g-1), indicating that inoculation of consortium Ⅱ effectively promoted substrate maturity and product quality. Moreover, this inoculation effectively optimized the bacterial communities, particularly the growth of Planococcus, Chelatococcus, and Chelativorans during the composting, which were involved in carbon and nitrogen conversion or HAC synthesis. Carbohydrate and amino acid metabolism, and membrane transport were predominant in the consortia-inoculated samples, with an increased gene abundance, suggesting that inoculation contributed to promoting the biodegradation of lignocellulose and the exchange of favorable factors. In conclusion, this study demonstrates that inoculating thermophilic bacterial consortia has a positive impact on enhancing the resource utilization efficiency of agricultural waste and improving the quality of compost products.

Bacterial diversity in water from Xifeng Hot Spring in China

The Xifeng Hot Spring is one of the eight largest hot springs in China, which is rich in radon gas and sulphur in karst scenery. Little is known about the microbiota structure in the spring. The water was collected from three sites containing the outlet of spring water discharge site (OWD), spring pool for tourist (SPT) and sewage effluent pool (SEP) in the Xifeng Hot Spring and further analyzed by culture-independent technique and culture-dependent method. A total of 57 phyla were identified from the water samples. The dominate phyla at OWD was Bacteroidetes (46.93%), while it was Proteobacteria in both sites of SEP and SPT with relative richness of 61.9% and 94.9%, respectively. Two bacteria, Deinococcus and Hymenobacter, that confirmed to be radiation-resistant, seven sulphur bacteria and three thermophilic bacteria were detected from Xifeng Hot Spring. Furthermore, it was found that genus Flavobacterium was susceptible to environmental change with abundance of 11 ~ 2825 times higher in OWD than the other two groups. Compared bacteria from the OWD group with that from 14 hot springs in six countries, total 94 unique genera bacteria were found out from the Xifeng Hot Spring including four thiometabolism-related bacteria (Propionispira, Desulforegula, Desulfobacter and Desulfococcus) and the thermophilic bacterium (Symbiobacterium). Using microbial culturing and isolation technology, sixteen strains were isolated from the water samples of three sites. The diversity of microbiota was abundant and variable along with the niche changed in conditions and surroundings. It indicated that numbers of valuable bacteria resources could be explored from the special surroundings of Xifeng Hot Spring.

Heterologous expression and biochemical characterization of novel multifunctional thermostable α-amylase from hot-spring metagenome

Hot-springs are regarded as the best source of industrially significant biocules and one of the unique locations for extremophiles. The α-amylase is one of the most important enzymes used in starch consuming industries, where the need of thermostability is paramount. In this study, the full metagenome sequences obtained from the soil of Tuwa hot-spring (Gujarat, India) were examined for the presence of several thermostable enzymes using bioinformatic techniques. The whole gene sequence for α-amylase was found from the metagenome. The α-amylase gene was amplified, cloned, and expressed in Escherichia coli and further characterized in vitro. The rm-α-amylase was found optimally active at 60 °C and at pH 6.0 and showed significantly high activity in 0.1 mM Co²⁺ as well as in other heavy metal ions without any effect on its thermostability. Apart from α-amylase activity the purified rm-α-amylase was also shown to hydrolyse agar, xylan, pectin, alginate and cellulose. To our knowledge, this is the first report of a new, multifunctional, thermostable amylase that was discovered from the hot-spring metagenomes. Owing to their multifunctionality, resilience towards high temperature and heavy metal ions, stability with solvents, additives and inhibitors, rm-α-amylase can be exploited for a variety of biotechnological applications.

The coupling system of magnetite-enhanced thermophilic hydrolysis-acidification and denitrification for refractory organics removal from anaerobic digestate food waste effluent (ADFE)

The aim of this study was to remove the refractory organics from high-temperature anaerobic digestate food waste effluent by the coupling system of hydrolysis-acidification and denitrification. Iron-based materials (magnetite, zero-valent iron, and iron-carbon) were used to enhance the performance of thermophilic hydrolysis-acidification. Compared with the control group, magnetite had the best strengthening effect, increasing volatile fatty acids concentration and fluorescence intensity of easily biodegradable organics in the effluent by 47.6 % and 108.4 %, respectively. The coupling system of magnetite-enhanced thermophilic hydrolysis-acidification and denitrification achieved a nitrate removal efficiency of 91.2 % (influent NO₃^--N was 150 mg L^-1), and reduced the fluorescence intensity of refractory organics by 33.8 %, compared with influent. Microbiological analysis indicated that magnetite increased the relative abundance of thermophilic hydrolytic acidifying bacteria, and coupling system enriched some genera simultaneously removing nitrate and refractory organics. This study provided fresh information on refractory organics and nitrogen removal of thermophilic wastewater biologically.

Isolation and characterization of potential multiple extracellular enzyme-producing bacteria from waste dumping area in Addis Ababa

Extremozymes are innovative and robust biocatalysts produced by various microorganisms from harsh environments. As thermophilic organisms can only develop in a few places, studying them in geothermal environments has provided new insights into the origins and evolution of early life and access to significant bio-resources with potential biotechnology applications. The work aimed to isolate and identify likely multiple extracellular enzyme-producing thermophilic bacteria from an Addis Ababa landfill (Qoshe). The streaking approach was used to purify 102 isolates acquired by serial dilution and spread plate method. The isolates were morphologically and biochemically characterized. Thirty-five cellulases, 22 amylase, 17 protease, and nine lipase-producing bacteria were identified using primary screening methods. Further secondary screening using Strain safety evaluation; two bacterial strains (TQ11 and TQ46) were identified. Based on morphological and biochemical tests, they were found to be gram-positive and rod-shaped. Furthermore, molecular identification and phylogenic analysis of selected promising isolates confirmed the identity of the isolates, Paenibacillus dendritiformis (TQ11) and Anoxybacillus flavithermus (TQ46). The results indicated that, multiple extracellular enzyme-producing thermophilic bacteria isolated from a waste dumping area in Addis Ababa offer useful features for environmental sustainability in a wide range of industrial applications due to their biodegradability and specialized stability under extreme conditions, increased raw material utilization, and decreased waste.

The removal of heavy metal pollution from wastewaters using thermophilic B. cereus SO-16 bacteria

In this study, bioaccumulation, remediation, tolerance, and effects of manganese ions (Mn(II)) and copper ions (Cu(II)) on antioxidant enzymes of thermophilic Bacillus cereus (B. cereus) SO-16 were investigated in detail. The findings of the study showed that Mn(II) was less toxic than Cu(II) to B. cereus SO-16. Moreover, B. cereus SO-16 was exhibited less tolerance to Mn(II) and Cu(II) ions in the liquid medium compared to the solid medium. The growth of bacteria was expressively effective for Mn(II) and Cu(II) concentrations of 2.5 mg/L at 24th h. The highest Mn(II) and Cu(II) bioaccumulation values after 48 h incubation of thermophilic B. cereus SO-16 were measured as 102.04 (24th h) and 87.96 (36th h) metal/dry bacteria weight. The change in morphology and functionality of B. cereus SO-16 after interaction with Mn(II) and Cu(II) was tested using various methods. The results indicated that B. cereus SO-16, a thermophilic bacterium, can be utilized in industrial wastewaters to recover and remediation of toxic metals.

In situ generated oxygen distribution causes maturity differentiation during electrolytic oxygen aerobic composting

Electrolytic oxygen aerobic composting (EOAC) is an effective treatment with greater technical superiority and cost advantages for organic solid waste using in situ electrolytic oxygen as a feasible strategy to replace conventional aeration. However, the unclear effects of distribution and variation of in situ electrolytic oxygen on compost maturation in different depth zones of EOAC need further exploration. This study demonstrated that the humification of organic matter was faster at the bottom than in the middle and at the top. The main reason was that the higher oxygen content and lower moisture content in the bottom promoted microbial degradation and heat production, resulting in higher temperatures. The microbial analysis showed that the abundance of typical thermophilic bacteria (such as Cerasibacillus, Lactobacillus, and Pseudogracilibacillus) that could promote compost maturation was higher at the bottom than in the middle and at the top. The finding provided in-depth molecular insights into differentiated humification from bottom to top in EOAC and revealed its further practical engineering applications.

Direct conversion of cellulose to L-lactic acid by a novel thermophilic Caldicellulosiruptor strain

Background

Consolidated bioprocessing (CBP) of lignocellulosic biomass to l-lactic acid using thermophilic cellulolytic/hemicellulolytic bacteria provides a promising solution for efficient lignocellulose conversion without the need for additional cellulolytic/hemicellulolytic enzymes. Most studies on the mesophilic and thermophilic CBP of lignocellulose to lactic acid concentrate on cultivation of non-cellulolytic mesophilic and thermophilic bacteria at temperatures of 30–55 °C with external addition of cellulases/hemicellulases for saccharification of substrates.

Results

l-Lactic acid was generated by fermenting microcrystalline cellulose or lignocellulosic substrates with a novel thermophilic anaerobic bacterium Caldicellulosiruptor sp. DIB 104C without adding externally produced cellulolytic/hemicellulolytic enzymes. Selection of this novel bacterium strain for lactic acid production is described as well as the adaptive evolution towards increasing the l-lactic acid concentration from 6 to 70 g/l on microcrystalline cellulose. The evolved strains grown on microcrystalline cellulose show a maximum lactic acid production rate of 1.0 g/l*h and a lactic acid ratio in the total organic fermentation products of 96 wt%. The enantiomeric purity of the l-lactic acid generated is 99.4%. In addition, the lactic acid production by these strains on several other types of cellulose and lignocellulosic feedstocks is also reported.

Conclusions

The evolved strains originating from Caldicellulosiruptor sp. DIB 104C were capable of producing unexpectedly large amounts of l-lactic acid from microcrystalline cellulose in fermenters. These strains produce l-lactic acid also from lignocellulosic feedstocks and thus represent an ideal starting point for development of a highly integrated commercial l-lactic acid production process from such feedstocks.

Integrating 16S rRNA amplicon metagenomics and selective culture for developing thermophilic bacterial inoculants to enhance manure composting

Composting is an important method for treating and recycling organic waste, and the use of microbial inoculants can increase the efficiency of composting. Herein, we illustrate an approach that integrate 16S rRNA amplicon metagenomics and selective culture of thermophilic bacteria for the development of inoculants to improve manure composting. The 16S rRNA amplicon sequencing analysis revealed that Firmicutes and Actinobacteria were dominant in the composting mixture, and that different microbial hubs succeeded during the thermophilic stage. All isolated thermophilic bacteria were affiliated with the order Bacillales, such as Geobacillus, Bacillus, and Aeribacillus. These isolated thermophilic bacteria were grouped into 11 phylotypes, which shared ＞99% sequence identity to 0.15% to 5.32% of 16S rRNA reads by the amplicon sequencing. Three of these phylotypes transiently enriched during the thermophilic stage. Six thermophilic bacteria were selected from the three phylotypes to obtain seven microbial inoculants. Five out of seven of the microbial inoculants enhanced the thermophilic stage of composting by 16.9% to 52.2%. Three-dimensional excitation emission matrix analysis further revealed that two inoculants (Thermoactinomyces intermedius and Ureibacillus thermophilus) stimulated humification. Additionally, the 16S rRNA amplicon sequencing analysis revealed that inoculation with thermophilic bacteria enhanced the succession of the microbial community during composting. In conclusion, 16S rRNA amplicon metagenomics is a useful tool for the development of microbial inoculants to enhance manure composting.

Identification, characterization and hydrolase producing performance of thermophilic bacteria: geothermal hot springs in the Eastern and Southeastern Anatolia Regions of Turkey

In the last two decades, researchers have increasingly focused on the rich microorganism-based diversity of natural hot spring sources to explore the benefits of thermophiles in industrial and biotechnological fields. Within the scope of this study, a total of 83 thermophilic Bacilli strains were isolated from 7 different geothermal hot springs (at temperatures ranging between 40 and 85 °C) located in the Eastern and Southeastern Anatolia Regions of Turkey. The physiological, morphological, biochemical and molecular properties of the isolates were determined. As a result of the 16S rRNA gene sequence analysis, 5 different species (Bacillus licheniformis, Bacillus sp., Bacillus subtilis, Geobacillus kaustophilus, and Weizmannia coagulans,) were identified. B. licheniformis and B. subtilis were the most frequently encountered species among those obtained from the researched hot spring sources. Phylogenetic analysis was conducted to evaluate the phylogenetic relationships of the isolated species. The results showed that there was no significant difference between the groups and the bacteria in terms of the locations or optimum temperatures of the isolates. The bacterial isolates were screened for amylase, cellulase, lipase and protease hydrolytic enzyme activities. The hydrolytic enzyme production potentials among the isolates were identified in 68 (82%) isolates for amylase, 34 (41%) for cellulase, 69 (83%) for lipase and 73 (88%) for protease. All isolates were found to have at least one or more extracellular enzyme activities. Additionally, it was determined that 27 of the existing isolates (32.8%) were able to produce all of the aforementioned hydrolytic enzymes.

Engineered bacteria for valorizing lignocellulosic biomass into bioethanol

Appropriate bioprocessing of lignocellulosic materials into ethanol could address the world's insatiable appetite for energy while mitigating greenhouse gases. Bioethanol is an ideal gasoline extender and is widely used in many countries in blended form with gasoline at specific ratios to improve fuel characteristics and engine performance. Although the bioethanol production industry has long been operational, finding a suitable microbial agent for the efficient conversion of lignocelluloses is still an active field of study. Among available microbial candidates, engineered bacteria may be promising ethanol producers while may show other desired traits such as thermophilic nature and high ethanol tolerance. This review provides the current knowledge on the introduction, overexpression, and deletion of the genes that have been performed in bacterial hosts to achieve higher ethanol yield, production rate and titer, and tolerance. The constraints and possible solutions and economic feasibility of the processes utilizing such engineered strains are also discussed.

Development of multi-species biofilm formed by thermophilic bacteria on stainless steel immerged in skimmed milk

Thermophilic bacteria, such as Bacillus licheniformis, Geobacillus stearothermophilus, Bacillus Subtilis and Anoxybacillus flavithermus, are detected frequently in milk powder products. Biofilms of those strains act as a major contamination to milk powder manufactures and pose potential risks in food safety. In this study, we explored the developing process of multi-species biofilm formed by the four thermophilic bacteria on stainless steel immerged in skimmed milk. The results showed that the thermophilic strains possessed strong capacities to decompose proteins and lactose in skimmed milk, and the spoilage effects were superimposed from multiple strains. B. licheniformis was the most predominant species in the mixed-species biofilm after 12-h incubation. From 24 h to 48 h, G. stearothermophilus occupied the highest proportion. Within the multi-species biofilm, competitive relation existed between B. licheniformis and G. stearothermophilus, while synergistic impacts were observed between B. licheniformis and A. flavithermus. The interspecies mutual influences on biofilm development provided important evidences for understanding colonization of the predominant thermophilic bacteria during milk powder processing.

Thermophilic bacteria combined with alkyl polyglucose pretreated mariculture solid wastes using as denitrification carbon source for marine recirculating aquaculture wastewater treatment

In marine recirculating aquaculture systems (RAS), efficient nitrogen removal is challenging due to the high NO₃^--N concentration, low organic matters content, and high salinity. In this study, mariculture solid wastes (MSW) acidogenic liquid pretreated by thermophilic bacteria (TB) combined with alkyl polyglucose (APG) was first used as carbon source for denitrification to remove NO₃^--N. TB + APG pretreatment could accelerate the hydrolysis of MSW, and the highest volatile fatty acids (VFAs) yield (40.3%) was obtained with TB + 0.2 g/g VSS APG pretreatment. MSW acidogenic liquid pretreated by TB + 0.2 g/g VSS APG was a reliable carbon source for denitrification, and the optimum COD/NO₃^--N ratio (C/N) was 8 with no residue of NO_x^--N. VFAs were more effectively utilized by denitrifiers than carbohydrate and protein. The high denitrification potential (P_DN) and denitrification rate (V_DN) indicated the higher denitrification ability at C/N of 8 using MSW acidogenic liquid as carbon source. The outcomes of this work could provide useful information for promoting technological innovation in marine RAS wastewater treatment.

Optimization, purification, and biochemical characterization of thermoalkaliphilic lipase from a novel Geobacillus stearothermophilus FMR12 for detergent formulations

This study was aimed to produce a high compatible thermoalkaliphilic lipase (TA) with detergents from new thermophilic bacterial strains utilizing fish wastes for industrial application. Among bacterial isolates, a new Geobacillus stearothermophilus FMR12 efficiently utilized fish wastes at a concentration of 20% (w/v), exhibiting highly lipolytic activity at extreme thermal and alkaline pH conditions. Optimized fermentation parameters of TA lipase production were ascertained, promoting the productivity of the TA lipase from 424 to 1038 U/ml. Purification results of TA lipase exposed prominent specific activity of 4788 U/mg, purification fold of 12.44, and 7.8% yield. The purified TA lipase demonstrated outstanding activity and stability in a temperature range of 40-95 °C and pH (4-11), revealing optimal activity at 70 °C and pH 9. The molecular weight of the enzyme was estimated to be 63 kDa. Compared to control, the TA lipase activity was promoted in the presence of calcium chloride. Likewise, Triton X-100 enhanced the activity of the TA lipase, recording 128% of the control enzyme. Interestingly, the TA lipase conserved higher than 90% of its activity after blending with commercial detergents, emphasizing its competence for detergent formulations.

Thermal pretreatment enhances the degradation and humification of lignocellulose by stimulating thermophilic bacteria during dairy manure composting

This study investigated the effect of thermal pretreatment (TP) on the lignocellulose degradation and humification during dairy manure composting and the underlying microbial mechanism. The results showed that TP accelerated temperature rise and elevated composting temperature by increasing 26% initial content of simple organics. The degradation of cellulose, hemicellulose and lignin was 78, 10 and 109% higher in thermal pretreatment composting (TPC) than traditional composting (TC), respectively. Moreover, TP significantly improved the humification degree of composts, as indicated by 14 and 38% higher humus content and humification indexes in TPC, respectively. 16S rRNA sequencing showed that TP increased the relative abundance of thermophilic bacteria in TPC, of which Thermobifida, Planifilum, Truepera and Thermomonospora were potentially involved in lignocellulose biodegradation and humification. Canonical correspondence analysis revealed that TP changed the main factor determining the bacterial community evolution from dissolved organic carbon (DOC) in TC to temperature in TPC.

Microbial diversity in relation to physico-chemical properties of hot water ponds located in the Yamunotri landscape of Garhwal Himalaya

The current study includes the assessment of physico-chemical characteristics along with the microbial diversity of hot water samples collected from three important sacred hot water springs of the Uttarakhand Himalaya close to the world-famous Hindu shrine Yamunotri temple. Hot water samples were collected for two consecutive years 2015-2016 in two sampling operations each year. A total of fifteen physico-chemical attributes of hot water were recorded. Microbes of hot water ponds were characterized by morphological, biochemical, MALDI-TOF MS, and molecular approaches. A total of twenty-two microbial strains were identified from the Surya Kund with water temperature ranging between 86 °C and 89 °C; twenty-two microbial strains were identified from the Draupadi Kund with water temperature ranging between 65 °C and 69 °C and twenty-one microbial strains were identified from the Yamunotri Tapt Kund with water temperature ranging between 45 °C and 48 °C during the study period. The present study on the assessment of physico-chemical characteristics and thermophilic microbial diversity of all the three hot water springs can be a useful reference for further studies on similar aspects in other parts of the Himalaya. The available data will also help to understand the reasons behind the curative properties of these hot water springs. This baseline information will also be instrumental for the conservation and management of these hot water springs.

Alkaline aided thermophiles pretreatment of waste activated sludge to increase short chain fatty acids production: Microbial community evolution by alkaline on hydrolysis and fermentation

Adding alkaline into an anaerobic waste activated sludge (WAS) fermentation with thermophilic bacteria pretreatment could efficiently improve short-chain fatty acids (SCFAs) accumulation to 3550 ± 120 mg COD/L. The acidification rate in combined test was 21.2%, while that was 15.6% and 10.7% in sole thermophilic bacteria pretreatment and control tests respectively. Four distinct groups of microbes could be identified with noticeable shifts using the combined pretreatments, and tremendous effects were analyzed on organic content especially of the soluble proteins and SCFAs concentrations. Particularly, alkaline addition would significantly change the functional microbial structures, including the decrease of Caloramator with the function of thermophilic proteolytic and the increase of Acidobacteria TM7 and Petrimonas sp. The results above suggested that alkaline addition could decrease the hydrolytic substances consume by thermotolerance bacteria and final improve SCFAs accumulation in fermentation process.

Utilization of methyltrioctylammonium chloride as new ionic liquid in pretreatment of sugarcane bagasse for production of cellulase by novel thermophilic bacteria

Fermentation of carbohydrates present in lignocellulosic (LC) biomass is facilitated by lignin removal, which is usually achieved by adopting various pretreatment methods to provide the enzymes proper access to their respective substrates. Pretreatment using ionic liquid (IL) is relatively recent advancement and considered as mild and green process. ILs can dissolve extensive quantities of biomass and depolymerize the cellulose. In this context, an abundantly available LC biomass, sugarcane bagasse (SB), was pretreated using alkali or with an IL, methyltrioctylammonium chloride, and was used for cellulase production from thermophilic bacteria. In all, 26 indigenously isolated thermophilic bacterial strains were quantitatively screened for cellulase production. 16S rDNA sequences of the promising isolates UE10 and UE27 revealed relatedness with Brevibacillus borstelensis, while the strain UE1 belonged to Aneurinibacillus thermoaerophilus. Cellulase production was compared by utilizing alkali pretreated and IL pretreated SB and the later was found more appropriate. UE1, UE10 and UE27 yielded 22.2, 22.18 and 33.3 IU mL^-1 of endoglucanase, respectively, by fermenting IL pretreated SB. The changes in SB structure after pretreatment were evaluated by scanning electron microscopy. This study demonstrated the potential of novel thermophilic bacterial strains to utilize IL pretreated SB for production of industrially important enzyme, cellulase.

Thermophilic waste air treatment of an airborne ethyl acetate/toluene mixture in a bubble column reactor: Stability towards temperature changes

Thermophilic waste air treatment in a lab-scale bubble column reactor (BCR) was used to remove an ethyl acetate/toluene mixture under both mesophilic and thermophilic conditions, at 30-50 °C. Additional tests, e.g., toluene mass transfer measurement and monitoring of microbial population development, explained the observed bioreactor response to the conducted loading tests and temperature changes. The maximum overall elimination capacity at thermophilic conditions (50 °C) was 136.9 g·m^-3 h^-1, however hysteresis in elimination capacity was observed in response to ascending/descending temperature and inlet concentration changes. Representatives of genera Cupriavidus, Variovorax and order Rhodospirillales were found to be predominant in the degrading microbial population, depending on the operating temperature. Thermobacillus and Blastocatella were abundant at high (50 °C) and low (30 °C) temperatures, respectively. The observed gradual shift in microbial population caused a small yet significant gradual change in developing a preference for toluene at the expense of ethyl acetate, which explains the observed hysteresis. Yet, the whole bioreactor removal efficiency remained similar at the same temperature, thus demonstrating the advantages of using thermophiles in bioreactors with temperature variation, such as robustness and flexibility.

Resonance assignment of the 128 kDa enzyme I dimer from Thermoanaerobacter tengcongensis

Enzyme I (EI) of the bacterial phosphotransferase system (PTS) utilizes phosphoenolpyruvate (PEP) as a source of energy in order to transport sugars across the cellular membrane. PEP binding to EI initiates a phosphorylation cascade that regulates a variety of essential pathways in the metabolism of bacterial cells. Given its central role in controlling bacterial metabolism, EI has been often suggested as a good target for antimicrobial research. Here, we report the ¹H_N, ¹⁵N, ¹³C', ¹H_methyl, and ¹³C_methyl chemical shifts of the 128 kDa homodimer EI from the thermophile Thermoanaerobacter tengcongensis. In total 79% of the expected backbone amide correlations and 80% of the expected methyl TROSY peaks from U-[²H, ¹³C, ¹⁵N], Ile^δ1-[¹³CH₃], Val-Leu-[¹³CH₃/¹²CD₃] labeled EI were assigned. The reported assignments will enable future structural studies aimed at illuminating the fundamental mechanisms governing long-range interdomain communication in EI and at indicating new therapeutic strategies to combat bacterial infections.

A comparative study of pig manure with different waste straws in an ectopic fermentation system with thermophilic bacteria during the aerobic process: Performance and microbial community dynamics

In the present study, ectopic fermentation systems were treated with both solid and liquid waste from livestock. Then, the various physicochemical properties and compositions of microbial communities in different waste straws treatments were compared. The addition of thermophilic bacteria was beneficial to the decomposition of litter, and it improved the fermentation process. Proteobacteria, Bacteroidetes, and Firmicutes were the predominant types in the fermentation vessels, and the presence of the phyla Proteobacteria and Bacteroidetes was correlated with factors prevailing in the mature phase. Furthermore, pig manure with sawdust, rape stem, and rice chaff and pig manure with sawdust, rice straw, and rice chaff vessels had higher concentrations of dissolved nitrogen, which were conducive to the conversion of fermentation wastes into useful fertilizer. These results demonstrate the feasibility of using rape stem and rice straw as padding materials during the treatment of both liquid and solid livestock waste in ectopic fermentation systems.

Role of thermophilic bacteria (Bacillus and Geobacillus) on crude oil degradation and biocorrosion in oil reservoir environment

Thermophilic bacterial communities generate thick biofilm on carbon steel API 5LX and produce extracellular metabolic products to accelerate the corrosion process in oil reservoirs. In the present study, nine thermophilic biocorrosive bacterial strains belonging to Bacillus and Geobacillus were isolated from the crude oil and produced water sample, and identified using 16S rRNA gene sequencing. The biodegradation efficiency of hydrocarbons was found to be high in the presence of bacterial isolates MN6 (82%), IR4 (94%) and IR2 (87%). During the biodegradation process, induction of the catabolic enzymes such as alkane hydroxylase, alcohol dehydrogenase and lipase were also examined in these isolates. Among them, the highest activity of alkane hydroxylase (130 µmol mg^-1 protein) in IR4, alcohol dehydrogenase (70 µmol mg^-1 protein) in IR2, and higher lipase activity in IR4 (60 µmol mg^-1 protein) was observed. Electrochemical impedance spectroscopy and X-ray diffraction data showed that these isolates oxidize iron into ferrous/ferric oxides as the corrosion products on the carbon steel surface, whilst the crude oil hydrocarbon served as a sole carbon source for bacterial growth and development in such extreme environments.

Production of highly thermo-tolerant laccase from novel thermophilic bacterium Bacillus sp. PC-3 and its application in functionalization of chitosan film

In this study, a novel thermophilic bacterial strain was isolated from Tattapani hot spring located in the Chhattisgarh state of India. The laccase was produced via submerged fermentation and purified by ammonium sulfate precipitation and anion exchange chromatography up to 13.7 fold. The 16S rRNA gene sequence and biochemical analysis revealed that the bacterial isolate is Bacillus sp. strain PC-3. The activity of extracellular crude laccase was determined to be 11.2 U/mL using 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) as a substrate. The SDS-PAGE revealed that the enzyme consists of single subunit with molecular size of 36 kDa. The laccase exhibited the maximum enzyme activity at temperature of 60°C and pH 7. Moreover, the laccase retained 99.1% of its original activity for 180 min and exhibited half-life of 3.75 h at 60°C. Similarly, the laccase retained 95% activity at pH 7 for 240 min and displayed significant activity at wider pH range. In addition, the laccase was used for functionalization of chitosan film and characterized for antioxidant and antimicrobial activity. Interestingly, the functionalized chitosan film showed the improved antioxidant and antimicrobial activity.

Hydrolytic Enzyme Production by Thermophilic Bacteria Isolated from Saudi Hot Springs

Hydrolytic enzyme production by thermophilic bacteria isolated from hot springs in the southern region of Saudi Arabia was investigated. The physical and chemical properties of the hot springs prove to be an important environment for hydrolytic-enzyme-producing thermophilic bacteria. Eighty-four bacterial isolates were obtained from three hot springs: Al-Majardah, Al-Khubah and Al-Ardah. Screening of the isolates for enzyme production indicated that 78 isolates showed activity for one or more enzymes. Molecular identification and phylogenic analysis of selected promising isolates confirmed the identity of the isolates as Bacillus aerius, Bacillus licheniformis and Bacillus sonorensis, which have potential to produce the target enzymes α-amylase, protease and lipase, respectively. Optimization of hydrolytic enzyme production by bacterial strains was investigated using kitchen waste as a cheap carbon energy source. Maximum enzyme production was achieved after 72 hours of incubation at the beginning of the stationary phase of growth. Enzyme production was dependent on the initial pH value in the range of pH 7.5-8.5 and an optimal incubation temperature of between 55-60°C. Enzyme production increased gradually in proportion to the kitchen waste concentration; whereas maximum lipase production was gained at 5.0% (w/v) kitchen waste, 7.0% (w/v) of waste was optimal for both α-amylase and protease productivity. The results indicated that hot springs in Saudi Arabia are a substantial source of thermophilic bacteria producing industrially important enzymes using cheap and unexploited waste.

Fermentation performance optimization in an ectopic fermentation system

Ectopic fermentation systems (EFSs) were developed for wastewater treatment. Previous studies have investigated the ability of thermophilic bacteria to improve fermentation performance in EFS. Continuing this research, we evaluated EFS performance using principle component analysis and investigated the addition of different proportions of cow dung. Viable bacteria communities were clustered and identified using BOX-AIR-based repetitive extragenic palindromic-PCR and 16S rDNA analysis. The results revealed optimal conditions for the padding were maize straw inoculated with thermophilic bacteria. Adding 20% cow dung yielded the best pH values (6.94-8.56), higher temperatures, increased wastewater absorption, improved litter quality, and greater microbial quantities. The viable bacteria groups were enriched by the addition of thermophilic consortium, and exogenous strains G21, G14, G4-1, and CR-15 were detected in fermentation process. The proportion of Bacillus species in treatment groups reached 70.37% after fermentation, demonstrating that thermophilic bacteria, especially Bacillus, have an important role in EFS, supporting previous predictions.

Thermostable enzymes and polysaccharides produced by thermophilic bacteria isolated from Bulgarian hot springs

Thermostable enzymes (thermozymes) have been recognized as extremophilic compounds with a greatest biotechnological importance in different industrial areas. Quite recently exopolysaccharides (EPSs) synthesized by thermophiles became an object of increased research interest due to their unique properties appropriate for some specific industrial needs. Thermophilic producers of biotechnologically valuable enzymes and novel EPS were isolated by our group from Bulgarian thermal springs with a diverse geotectonic origin and different water properties. Laboratory reactor processes for their production were developed in batch and continuous cultures. Some of the synthesized thermostable enzymes were among the first described in their groups, for example, the single known thermostable gellan lyase that demonstrated specific activity higher than that of the mesophilic enzymes. Isolated by us thermostable xylanase was able to degrade more than 60% of beechwood xylan in a coprocess with an archaeal β-xylosidase. Lipase purified by us was active between 55 and 90°C with an optimum at 75-80°C in a large pH range. It was able to degrade a broad range of substrates. Isolates from Bulgarian hot springs synthesized EPS with novel composition and high thermostability. Thus, Bulgarian hot springs harbor a wide set of thermophilic producers of novel enzymes and EPS with potential for a large number of biotechnological applications.

1H, 15N, 13C backbone resonance assignment of the C-terminal domain of enzyme I from Thermoanaerobacter tengcongensis

Phosphoenolpyruvate binding to the C-terminal domain (EIC) of enzyme I of the bacterial phosphotransferase system (PTS) initiates a phosphorylation cascade that results in sugar translocation across the cell membrane and controls a large number of essential pathways in bacterial metabolism. EIC undergoes an expanded to compact conformational equilibrium that is regulated by ligand binding and determines the phosphorylation state of the overall PTS. Here, we report the backbone ¹H, ¹⁵N and ¹³C chemical shift assignments of the 70 kDa EIC dimer from the thermophilic bacterium Thermoanaerobacter tengcongensis. Assignments were obtained at 70 °C by heteronuclear multidimensional NMR spectroscopy. In total, 90% of all backbone resonances were assigned, with 264 out of a possible 299 residues assigned in the ¹H-¹⁵N TROSY spectrum. The secondary structure predicted from the assigned backbone resonance using the program TALOS+ is in good agreement with the X-ray crystal structure of T. tengcongensis EIC. The reported assignments will allow detailed structural and thermodynamic investigations on the coupling between ligand binding and conformational dynamics in EIC.

In vivo selection of sfGFP variants with improved and reliable functionality in industrially important thermophilic bacteria

BACKGROUND

Fluorescent reporter proteins (FP) have become an indispensable tool for the optimization of microbial cell factories and in synthetic biology per se. The applicability of the currently available FPs is, however, constrained by species-dependent performance and misfolding at elevated temperatures. To obtain functional reporters for thermophilic, biotechnologically important bacteria such as Parageobacillus thermoglucosidasius, an in vivo screening approach based on a mutational library of superfolder GFP was applied.

RESULTS

Flow cytometry-based benchmarking of a set of GFPs, sfGFPs and species-specific codon-optimized variants revealed that none of the proteins was satisfyingly detectable in P. thermoglucosidasius at its optimal growth temperature of 60 °C. An undirected mutagenesis approach coupled to fluorescence-activated cell sorting allowed the isolation of sfGFP variants that were extremely well expressed in the chassis background at 60 °C. Notably, a few nucleotide substitutions, including silent mutations, significantly improved the functionality and brightness. The best mutant sfGFP(N39D/A179A) showed an 885-fold enhanced mean fluorescence intensity (MFI) at 60 °C and is the most reliable reporter protein with respect to cell-to-cell variation and signal intensity reported so far. The in vitro spectral and thermostability properties were unaltered as compared to the parental sfGFP protein, strongly indicating that the combination of the amino acid exchange and an altered translation or folding speed, or protection from degradation, contribute to the strongly improved in vivo performance. Furthermore, sfGFP(N39D/A179A) and the newly developed cyan and yellow derivatives were successfully used for labeling several industrially relevant thermophilic bacilli, thus proving their broad applicability.

CONCLUSIONS

This study illustrates the power of in vivo isolation of thermostable proteins to obtain reporters for highly efficient fluorescence labeling. Successful expression in a variety of thermophilic bacteria proved that the novel FPs are highly suitable for imaging and flow cytometry-based studies. This enables a reliable cell tracking and single-cell-based real-time monitoring of biological processes that are of industrial and biotechnological interest.

Conversion of cellulose and hemicellulose of biomass simultaneously to acetoin by thermophilic simultaneous saccharification and fermentation

BACKGROUND

Acetoin (3-hydroxy-2-butanone), the precursor of biofuel 2,3-butanediol, is an important bio-based platform chemical with wide applications. Fermenting the low-cost and renewable plant biomass is undoubtedly a promising strategy for acetoin production. Isothermal simultaneous saccharification and fermentation (SSF) is regarded as an efficient method for bioconversion of lignocellulosic biomass, in which the temperature optima fitting for both lignocellulose-degrading enzymes and microbial strains.

RESULTS

A thermotolerant (up to 52 °C) acetoin producer Bacillus subtilis IPE5-4 which simultaneously consumed glucose and xylose was isolated and identified. By compound mutagenesis, the mutant IPE5-4-UD-4 with higher acetoin productivity was selected. When fermenting at 50 °C in a 5-L bioreactor using glucose as the feedstock by strain IPE5-4-UD-4, the acetoin concentration reached 28.83 ± 0.91 g L^-1 with the acetoin yield and productivity of 0.34 g g^-1 glucose and 0.60 g L^-1 h^-1, respectively. Furthermore, an optimized and thermophilic SSF process operating at 50 °C was conducted for acetoin production from alkali-pretreated corncob (APC). An acetoin concentration of 12.55 ± 0.28 g L^-1 was achieved by strain IPE5-4-UD-4 in shake flask SSF, with the acetoin yield and productivity of 0.25 g g^-1 APC and 0.17 g L^-1 h^-1. Meanwhile, the utilization of cellulose and hemicellulose in the SSF approach reached 96.34 and 93.29%, respectively. When further fermented at 50 °C in a 5-L bioreactor, the concentration of acetoin reached the maximum of 22.76 ± 1.16 g L^-1, with the acetoin yield and productivity reaching, respectively, 0.46 g g^-1 APC and 0.38 g L^-1 h^-1. This was by far the highest acetoin yield in SSF from lignocellulosic biomass.

CONCLUSIONS

This thermophilic SSF process provided an efficient and economical route for acetoin production from lignocellulosic biomass at ideal temperature for both enzymatic hydrolysis and microbial fermentation.

Prospecting Agro-waste Cocktail: Supplementation for Cellulase Production by a Newly Isolated Thermophilic B. licheniformis 2D55

Bacteria isolated from thermophilic environment that can produce cellulase as well as utilise agro-waste biomass have a high potential for developing thermostable cellulase required in the biofuel industry. The cost for cellulase represents a significant challenge in converting lignocellulose to fermentable sugars for biofuel production. Among three potential bacteria examined, Bacillus licheniformis 2D55 (accession no. KT799651) was found to produce the highest cellulolytic activity (CMCase 0.33 U/mL and FPase 0.09 U/mL) at 18–24 h fermentation when grown on microcrystalline cellulose (MCC) as a carbon source in shake flask at 50 °C. Cellulase production process was further conducted on the untreated and NaOH pretreated rice straw (RS), rice husk (RH), sugarcane bagasse (BAG) and empty fruit bunch (EFB). Untreated BAG produced the highest FPase (0.160 U/mL), while the highest CMCase (0.150 U/mL) was supported on the pretreated RH. The mixture of untreated BAG and pretreated RH as agro-waste cocktail has remarkably improved CMCase (3.7- and 1.4-fold) and FPase (2.5- and 11.5-fold) compared to the untreated BAG and pretreated RH, respectively. The mechanism of cellulase production explored through SEM analysis and the location of cellulase enzymes of the isolate was also presented. Agro-waste cocktail supplementation provides an alternative method for an efficient production of cellulase.

Determining the roles of the three alcohol dehydrogenases (AdhA, AdhB and AdhE) in Thermoanaerobacter ethanolicus during ethanol formation

Thermoanaerobacter ethanolicus is a promising candidate for biofuel production due to the broad range of substrates it can utilize and its high ethanol yield compared to other thermophilic bacteria, such as Clostridium thermocellum. Three alcohol dehydrogenases, AdhA, AdhB and AdhE, play key roles in ethanol formation. To study their physiological roles during ethanol formation, we deleted them separately and in combination. Previously, it has been thought that both AdhB and AdhE were bifunctional alcohol dehydrogenases. Here we show that AdhE has primarily acetyl-CoA reduction activity (ALDH) and almost no acetaldehyde reduction (ADH) activity, whereas AdhB has no ALDH activity and but high ADH activity. We found that AdhA and AdhB have similar patterns of activity. Interestingly, although deletion of both adhA and adhB reduced ethanol production, a single deletion of either one actually increased ethanol yields by 60-70%.

OPTIMIZATION OF ALKALINE Α-AMYLASE PRODUCTION BY THERMOPHILIC BACILL US SUBTILIS

Background:

Starch-degrading amylase enzyme is important in biotechnological applications as food, fermentation, textile, paper and pharmaceutical purposes. The aim of current study to isolate alkaline thermostable α-amylase bacteria and then study the composition of medium and culture conditions to optimize cells growth and a-amylase production.

Materials and Methods:

Thermophilic amylase producing bacterium was isolated from local hot water-springs in Gazan city Saudi Arabia.

Results:

Phylogenetic analysis of 16 S rRNA sequence for the strain revealed that the strain have the same sequence of Bacillus subtilis. Maximum amylase production was observed, when B. subtilis cultured in medium containing starch at concentration 0.5%, and 10 g/L peptones as nitrogen source at pH 8.5 in when it was incubated for 48 h at 45°C.

Conclusion:

An amylase-producing bacterium were isolated from hot-spring water and was identified as B. subtilis. Amylase produced from B.subtilis had optimum temperature 45°C and pH 8.5 in shaking media.

An improved agar medium for growth of Geobacillus thermoglucosidarius strains

Geobacillus species have potential applications in many biotechnological processes. They are fastidious in their vitamin and amino acid requirements. A new semi-defined agar medium (SDM) was developed which gave consistently high viable cell counts of various G. thermoglucosidasius strains (5×10⁸-6×10⁸cfu/ml) under aerobic conditions at 70°C.

In vitro synthesis of polyhydroxyalkanoates using thermostable acetyl-CoA synthetase, CoA transferase, and PHA synthase from thermotorelant bacteria

Thermostable enzymes are required for the rapid and sustainable production of polyhydroxyalkanoate (PHA) in vitro. The in vitro synthesis of PHA using the engineered thermostable synthase PhaC1_SG(STQK) has been reported; however, the non-thermostable enzymes acetyl-CoA synthetase (ACS) and CoA transferase (CT) from mesophilic strains were used as monomer-supplying enzymes in this system. In the present study, acs and ct were cloned from the thermophilic bacteria Pelotomaculum thermopropionicum JCM10971 and Thermus thermophilus JCM10941 to construct an in vitro PHA synthesis system using only thermostable enzymes. ACS from P. thermopropionicum (ACS_Pt) and CT from T. thermophilus (CT_Tt) were confirmed to have high thermostability, and their optimal temperatures were around 60°C and 75°C, respectively. The in vitro PHA synthesis was successfully performed by ACS_Pt, CT_Tt, PhaC1_SG(STQK), and poly(3-hydroxybutyrate) [P(3HB)] was synthesized at 45°C. Furthermore, the yields of P(3HB) and P(lactate-co-3HB) at 37°C were 1.4-fold higher than those of the in vitro synthesis system with non-thermostable ACS and CT from mesophilic strains. Overall, the thermostable ACS and CT were demonstrated to be useful for the efficient in vitro PHA synthesis at relatively high temperatures.

Strain and bioprocess improvement of a thermophilic anaerobe for the production of ethanol from wood

BACKGROUND

The thermophilic, anaerobic bacterium Thermoanaerobacterium saccharolyticum digests hemicellulose and utilizes the major sugars present in biomass. It was previously engineered to produce ethanol at yields equivalent to yeast. While saccharolytic anaerobes have been long studied as potential biomass-fermenting organisms, development efforts for commercial ethanol production have not been reported.

RESULTS

Here, we describe the highest ethanol titers achieved from T. saccharolyticum during a 4-year project to develop it for industrial production of ethanol from pre-treated hardwood at 51-55 °C. We describe organism and bioprocess development efforts undertaken to improve ethanol production. The final strain M2886 was generated by removing genes for exopolysaccharide synthesis, the regulator perR, and re-introduction of phosphotransacetylase and acetate kinase into the methyglyoxal synthase gene. It was also subject to multiple rounds of adaptation and selection, resulting in mutations later identified by resequencing. The highest ethanol titer achieved was 70 g/L in batch culture with a mixture of cellobiose and maltodextrin. In a "mock hydrolysate" Simultaneous Saccharification and Fermentation (SSF) with Sigmacell-20, glucose, xylose, and acetic acid, an ethanol titer of 61 g/L was achieved, at 92 % of theoretical yield. Fungal cellulases were rapidly inactivated under these conditions and had to be supplemented with cellulosomes from C. thermocellum. Ethanol titers of 31 g/L were reached in a 100 L SSF of pre-treated hardwood and 26 g/L in a fermentation of a hardwood hemicellulose extract.

CONCLUSIONS

This study demonstrates that thermophilic anaerobes are capable of producing ethanol at high yield and at titers greater than 60 g/L from purified substrates, but additional work is needed to produce the same ethanol titers from pre-treated hardwood.

Model of the sewage sludge-straw composting process integrating different heat generation capacities of mesophilic and thermophilic microorganisms

A mathematical model integrating 11 first-order differential equations describing the dynamics of the aerobic composting process of sewage sludge was proposed. The model incorporates two microbial groups (mesophiles and thermophiles) characterized by different capacities of heat generation. Microbial growth rates, heat and mass transfer and degradation kinetics of the sewage sludge containing straw were modeled over a period of 36days. The coefficients of metabolic heat generation for mesophiles were 4.32×10(6) and 6.93×10(6)J/kg, for winter and summer seasons, respectively. However, for thermophiles, they were comparable for both seasons reaching 10.91×10(6) and 10.51×10(6)J/kg. In the model, significant parameters for microbial growth control were temperature and the content of easily hydrolysable substrate. The proposed model provided a satisfactory fit to experimental data captured for cuboid-shaped bioreactors with forced aeration. Model predictions of specific microbial populations and substrate decomposition were crucial for accurate description and understanding of sewage sludge composting.

Three-dimensional fluorescence excitation-emission matrix (EEM) spectroscopy with regional integration analysis for assessing waste sludge hydrolysis treated with multi-enzyme and thermophilic bacteria

The hydrolysis effect of waste sludge after multi-enzyme and thermophilic bacteria pretreatments is investigated using excitation-emission matrix (EEM) with fluorescence regional integration (FRI) in this study. The compositional characteristics of extracellular polymeric substances (EPS) and dissolved organic matters (DOM) were analyzed to evaluate the sludge disintegration. The EPS and cell wall in sludge were disrupted after hydrolysis which led to carbohydrate, protein and soluble chemical oxygen demand (SCOD) of DOM increasing in sludge supernatant. The bio-degradability level in the extracted fractions of EPS and DOM depending on the fluorescence zones was found after hydrolysis. The highest proportion of percent fluorescence response (Pi,n) in EPS and DOM was soluble microbial by-product and humic acid-like organics. A significant increase of humic acid-like organics in DOM after thermophilic bacteria hydrolysis was obtained. The assessment of hydrolysis using EEM coupled with FRI provided a new insight toward the bio-utilization process of waste sludge.

Thermophilic hydrogen production from sludge pretreated by thermophilic bacteria: analysis of the advantages of microbial community and metabolism

In this study, the effects of thermophilic bacteria pretreatment and elevated fermentation temperature on hydrogen production from sludge were examined. The highest hydrogen yield of 19.9mlH2g(-1) VSS was achieved at 55°C by using pretreated sludge, which was 48.6% higher than raw sludge without pretreatment, and 28.39% higher than when fermented at 35°C. To explore the internal factors of this superior hydrogen production performance, the microbial community and the metabolism analysis were performed by using high-throughput sequencing and excitation-emission matrix. The pretreated sludge showed better utilization of dissolved organic matter and less inhibition of metabolism, especially at thermophilic condition. The 454 sequencing data indicated that microbial abundance was distinctly reduced and extremely high proportion of hydrogen-producing bacteria was found in the thermophilic community (Thermoanaerobacterium accounted for 93.75%). Thus, the pretreated sludge and thermophilic condition showed significant advantages in the hydrogen production using waste sludge as substrate.

Screening and characterization of extracelluar L-asparaginase producing Bacillus subtilis strain hswx88, isolated from Taptapani hotspring of Odisha, India

OBJECTIVE

To screen and isolate an eco-friendly, a thermophilic and potent L-asparaginase producing bacterium, with novel immunological properties that may obviates hypersensitivity reactions.

METHODS

In the present study bacterial strain isolated for extracellular L-asparaginase production from hotspring, identified by morphological, biochemical and physiological tests followed by 16S rDNA technology and the L-asparaginase production ability was tested by both semi quantitative and quantitative enzymatic assay.

RESULTS

The bacterial strain was identified as Bacillus subtilis strain hswx88 (GenBank Accession Number: JQ237656.1). The extracellular enzyme yielding capacity isolate Bacillus subtilis strain hswx88 (23.8 IU/mL) was found to be 1.7 and 14.5 times higher than the reference organism Pectobacterium carotovorum MTCC 1428 (14.2 IU/mL) and Bacillus sp. BCCS 034 (1.64 IU/mL).

CONCLUSION

The isolate is eco-friendly and useful to produce bulk quantity of extracellular, thermophilic L-asparaginase for the treatment of various tumor cases and for preparation of acrylamide free fry food preparation.

Extraction of Copper from Malanjkhand Low-Grade Ore by Bacillus stearothermophilus

Thermophilic bacteria are actively prevalent in hot water springs. Their potential to grow and sustain at higher temperatures makes them exceptional compare to other microorganism. The present study was initiated to isolate, identify and determine the feasibility of extraction of copper using thermophilic heterotrophic bacterial strain. Bacillus stearothermophilus is a thermophilic heterotrophic bacterium isolated from hot water spring, Atri, Orissa, India. This bacterium was adapted to low-grade chalcopyrite ore and its efficiency to solubilize copper from Malanjkhand low-grade ore was determined. The low-grade copper ore contains 0.27% Cu, in which the major copper-bearing mineral is chalcopyrite associated with other minerals present as minor phase. Variation in parameters such as pulp-density and temperatures were studied. After 30 days of incubation, it was found that Bacillus stearothermophilus solubilize copper up to 81.25% at pH 6.8 at 60°C.