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![Glucose metabolic pathways in Zymomonas mobilis (GK: glucokinase, GPDH: glucose-6-phosphate dehydrogenase , PGL: phosphogluconolactonase, EDD: 6-phosphogluconate dehydratase, KDPG: 2-keto-3-deoxy-6-phosphogluco- nate, GAPDH: glyceraldehydes-3-phosph- ate dehydrogenase, PGK: phosphoglycerate kinase, PGM: phosphoglyceromutase, ENO: enolase, PYK: pyruvate kinase, PDC: pyruvate decarboxylase) (adapted from Koutinas et al. [91]).](profile/Seraphim-Papanikolaou/publication/284559968/figure/fig1/AS:358268900790272@1462429370410/Glucose-metabolic-pathways-in-Zymomonas-mobilis-GK-glucokinase-GPDH.png)
Glucose metabolic pathways in Zymomonas mobilis (GK: glucokinase, GPDH: glucose-6-phosphate dehydrogenase , PGL: phosphogluconolactonase, EDD: 6-phosphogluconate dehydratase, KDPG: 2-keto-3-deoxy-6-phosphogluco- nate, GAPDH: glyceraldehydes-3-phosph- ate dehydrogenase, PGK: phosphoglycerate kinase, PGM: phosphoglyceromutase, ENO: enolase, PYK: pyruvate kinase, PDC: pyruvate decarboxylase) (adapted from Koutinas et al. [91]).
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The majority of environmental problems arise from the use of conventional energy sources. The liability of such problems along with the reduction of fossil energy resources has led to the global need for alternative renewable energy sources. Using renewable biofuels as energy sources is of remarkable and continuously growing importance. Producing b...
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... an onset of biosynthesis of the enzymes responsible for the gluconeogenesis [86]. According to Piškur et al. [84] the metabolism in Crabtree-positive yeast strains changes after exhaustion of glucose and accumulation of ethanol, with the requirement of certain transcription factors and enzymes. The (ethanol) "make-accumulate-consume" strategy ( Fig. 2 [32]) re- lies on the evolution of Saccharomyces against its competitors as ethanol is toxic to most other microbes. Therefore it is con- sidered that in a (nonaseptic) sugar-rich environment, Saccha- romyces kills its competitors by producing ethanol, but can also Figure 2. Glucose and ethanol assimilation by Saccharomyces cerevisiae under ...
Context 2
... an onset of biosynthesis of the enzymes responsible for the gluconeogenesis [86]. According to Piškur et al. [84] the metabolism in Crabtree-positive yeast strains changes after exhaustion of glucose and accumulation of ethanol, with the requirement of certain transcription factors and enzymes. The (ethanol) "make-accumulate-consume" strategy ( Fig. 2 [32]) re- lies on the evolution of Saccharomyces against its competitors as ethanol is toxic to most other microbes. Therefore it is con- sidered that in a (nonaseptic) sugar-rich environment, Saccha- romyces kills its competitors by producing ethanol, but can also Figure 2. Glucose and ethanol assimilation by Saccharomyces cerevisiae under ...
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... Significant correlations were found between the intermediate products of starch degradation, such as 6phosphogluconic acid and D-gluconic acid, and the varied abundance of Conexibacter, Fibrella, Valsa, Ruminiclostridiuma, which are known to promote the glycolysis and gluconogenesis pathways (Silver et al., 2014). Valsa, belonging to the Ascomycetes, Frontiers in Bioengineering and Biotechnology frontiersin.org is known to decompose organic matter, forming glucose-6-phosphate (G6P), and subsequently isomerizing G6P to synthesize enzymes capable of decomposing starch (Sarris and Papanikolaou, 2016). ...
Tobacco, a vital economic crop, had its quality post-curing significantly influenced by starch content. Nonetheless, the existing process parameters during curing were inadequate to satisfy the starch degradation requirements. Microorganisms exhibit inherent advantages in starch degradation, offering significant potential in the tobacco curing process. Our study concentrated on the microbial populations on the surface of tobacco leaves and in the rhizosphere soil. A strain capable of starch degradation, designated as BS3, was successfully isolated and identified as Bacillus subtilis by phylogenetic tree analysis based on 16SrDNA sequence. The application of BS3 on tobacco significantly enhanced enzyme activity and accelerated starch degradation during the curing process. Furthermore, analyses of the metagenome, transcriptome, and metabolome indicated that the BS3 strain facilitated starch degradation by regulating surface microbiota composition and affecting genes related to starch hydrolyzed protein and key metabolites in tobacco leaves. This study offered new strategies for efficiently improving the quality of tobacco leaves.
... The transformation of cellulose present in lignocellulosic feedstocks into bioethanol constitutes a substantial strategy for energy exploitation [7][8][9]. Cellulosic ethanol is considered as a highly promising renewable fuel due to its elevated octane number, heat of vaporization, and compatibility with motor vehicles [10]. Consequently, the conversion of abundant, low-cost lignocellulosic feedstocks into cellulose ethanol holds paramount scientific significance in mitigating the fossil fuel crisis and achieving sustainable circular agriculture development [11][12][13]. ...
The economy of the bioethanol production process can be improved by increasing the initial solid content and reducing the reaction time. The enzymatic approach utilizing intermittent ball milling has been proposed as a viable solution to tackle these challenges effectively. This study demonstrated that intermittent ball milling during high-solids enzymatic hydrolysis for a duration of 12 h showed a significantly higher total sugar yield, with an increase of 25.8% compared to continuous ball milling enzymatic hydrolysis method. The subsequent investigation comprehensively examined the impact of multi-conditional parameter variations on sugar yield during intermittent ball milling. The orthogonal experiment resulted in the determination of optimal process parameters, including a solid–liquid ratio of 25%, ball milling time (per cycle) of 5 min, ball milling frequency of 50 Hz, 6 balls used during the process, and an incubation temperature of 50℃ under optimized conditions. The conditions led to the achievement of a total reducing sugar concentration of 103.8 g/L, a total sugar yield of 415.1 mg/g, and an enzymatic hydrolysis yield of 72.4%. The optimized intermittent ball milling process exhibited superior hydrolysis yield and shorter reaction time compared to other enzymatic methods with untreated biomass. This study holds significant implications for the eventual industrialization of bioethanol refinement.
... Since OMWW is sugar deficient, blends of external glucose must be evaluated for the process's economic efficiency. Instead of expensive commercial glucose, wastewater rich in concentrated sugar diluted with OMWW can provide a more economically feasible solution [67]. The Saccharomyces cerevisiae MAK-1 has shown ability to grow in medium with high quantities of phenolic compounds [68]. ...
Every year, significant amounts of money and resources are invested worldwide to clean billions of litres of wastewater, which requires a substantial amount of energy. Olive mill wastewater (OMWW) is a valuable resource that can be valorized by several bioprocesses due to its high concentration of carbon sources, organic compounds and minerals. Therefore it is necessary to extend the use of low-cost biotechniques that reduce organic load and generate capital from value-added products. Since OMWW contains low to moderate amounts of nitrogen, sugar, volatile acid, polyalcohol and fat, it can be used as a feedstock to produce biofuels and other value-added products. However, the OMWW composition and biovalorization potential is influenced by various factors, such as olive variety, fruit ripeness, water use, extraction process (press or centrifuge), etc. OMWW also offers resources that can be used to improve soil fertility and productivity, due to high concentration of organic matter and the availability of numerous minerals, most notably potassium. However, microbial growth suppression by phenolic chemicals, acidic pH, low nitrogen content, etc., are challenging obstacles. Several biological approaches have been explored to reduce the organic load of OMWW and biovalorize it into valuable products such as biofuels and manure. This chapter discusses the sources, composition and biovalorization potential of OMWW for biofuel (bioethanol, biodiesel, biohydrogen, biomethane) and manure production. The focus has been placed on the most recent information available to produce biofuel and manure, as well as the accompanying challenges and their potential sustainable solutions to increase the economic viability of OMWW and green approaches to a circular economy.
... Hexoses and pentoses are monomeric sugars fermented during this process to produce alcohols, lactic acid, and other desirable products [56,66]. Various eukaryotic microbes viz Candida tropicalis, Candida oleophila, Hanseniaspora spp., Saccharomyces uvarum, Saccharomyces cerevisiae, Saccharomyces rouxii, Kluyveromyces lactis, Kluyveromyces fragilis, Mucor rouxianus and prokaryotic microbes Thermoanaerobacter ethanolicus, Clostridium thermosaccharolyticum, Clostridium sporogenes, Clostridium acetobutylicum, Zymomonas mobilis, and Bacillus stearothermophilus have been investigated for fermentation to produce bioethanol [110]. The performance factors for fermentation include temperature range, specificity, osmotic tolerance, genetic stability, growth rate, pH range, productivity, yield, inhibitor tolerance, and alcohol tolerance [15]. ...
The global demand for ethanol is rising tremendously because of fast industrialization and population expansion. The increased attention gained by ethanol is due to its application as a transport fuel because it is renewable, sustainable, eco-friendly, carbon neutral, and has a high-octane rating. The processes involved in its production include treatment and hydrolysis of substrates when starchy and lignocellulosic materials are used, microbial fermentation of substrates to bioethanol, and downstream processes such as distillation. The various steps are delineated in this chapter, but more consideration is given to the microbial fermentation of diverse substrates. Also presented in the chapter are the critical steps in adopting emerging technologies to improve the overall conversion system. Modeling and optimizing the pertinent operating variables involved in microbial fermentation to obtain bioethanol can make the process cost-effective and offer insight into understanding the behavior of the process. The benefits and downsides of some response surface methodology (RSM) screening approaches were discussed. The machine-learning techniques commonly used to model biochemical systems were also discussed extensively. It was noted that these data-mining techniques are better at handling the nonlinearity and multivariate nature of the microbial fermentation process for bioethanol production than the non-data-mining techniques, such as RSM.KeywordsBioethanolFermentationModelingOptimizationMachine learning technologyMicrobesEnzymesHydrolysisSaccharificationPretreatment
... Therefore, it can be inferred that dilute tetraoxosulphate (vi) acid was more effective in hydrolysis of bagasse than sodium hydroxide solution. The pretreatment (hydrolysis) process breakdown lignin and hemicellulose, and at the same time reduces cellulose crystallinity, and increases the porosity of the bagasse as noted by researchers [12,14,28]. Table 2 reveals the characteristics of the Aspergillus niger used for the saccharification of bagasse. ...
... It was noted that A. niger has black mycelium with septate hyphae, long and smooth conidiophores, with a large and round head on potato dextrose [20]. The Aspergillus niger produced cellulase enzymes that catalysed the conversion of cellulose in bagasse into fermentable sugars [14,28]. The fermentable sugars produced were utilized by Saccharomyces cerevisiae for ethanol production.Saccharomyces cerevisiae is able to produced ethanol due to the presence of pyruvate decarboxylase and alcohol dehydrogenase which are key enzymes in ethanol formation, as reported by Gunasekaran and Chandra [29]. ...
Plant biomass can be utilized to produce bioethanol, because they are abundantly available in nature. The cost of ethanol production from lignocellulosic materials is relatively high with low yield. But this can be solved by strain improvement processes. This study is aimed at evaluate bioethanol production potential of improved strains of Saccharomyces cerevisiae developed through random mutagenesis. Bagasse was hydrolysed with 1% NaOH and 1.0M H 2 SO 4 respectively for five days. 17 The hydrolysed bagasse was saccharified using Aspergillus niger isolated from soil samples. Saccharomyces cerevisiae isolated from locally produced wines; sorghum (burukutu) oil palm wine (emu) and raphia palm wine (oguro) with the highest ethanol production (5.0g/ml) were used, and then treated with physical mutagen (ultraviolet light) and chemical mutagens (Acridine dye, Bromo acetaldehyde, dithiothreitol, Ketoconazole and Nitrous acid) respectively to develop mutant with high ethanol producing efficiency under varied operational parameters. Three mutant strains of Saccharomyces cerevisiae namely;-SUV, SCD and SCK produced higher volumes of ethanol (7.5 g/ml, 9.8 g/ml, 11.2 g/ml respectively). SCD and SCK were able to grow at 25% ethanol concentration indicating that they had higher ethanol tolerance ability than the other strains. The optimum temperature and pH for ethanol production by all the strains were 35 0 C and 6.0 respectively. The improved strains of Saccharomyces cerevisiae developed through random mutation techniques had produced more ethanol from the bagasse than the wild-type.
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... As the main volatile components, the concentration of ethanol M and ethanol D increased by 4.13 and 12.05 times, respectively. As an important member of alcohol family, ethanol is mainly produced by a series of reactions in the process of microbial glycolysis (also known as Embden-Meyerhof-Parnas pathway) (Sarris & Papanikolaou, 2016). It is usually regarded as a landmark compound of pollution or fermentation of fruits and vegetables. ...
... The yeasts grown in the absence of EO were considered as the control. Naturally, despite aerobiosis, the microorganism proceeded with glucose fermentation that resulted in the accumulation of ethanol quantities into the culture medium [Crabtree positive yeast-see, i.e., [35][36][37][38]]. As such, the biomass and ethanol produced, as well as the consumption of glucose, were examined. ...
In this study, the essential oil (EO) from the peel of the Greek citrus hybrid Citrus sinensis cv New Hall - Citrus aurantium was studied in terms of its antimicrobial properties as well as its effect on Saccharomyces cerevisiae. According to the analysis of the EO, 48 compounds are contained in it, with the main compounds being limonene, β-pinene, myrcene, α-pinene, valencene, and α-terpineol. As regards its antimicrobial properties, the EO was evaluated against nine human pathogenic microorganisms, six bacteria, and three fungi. Taking the results into account, it was apparent that Gram-negative bacteria were the most susceptible to the addition of the EO, followed by the Gram-positive bacteria, and finally the examined yeasts. The minimum inhibitory concentrations were found to be lower compared to other studies. Finally, the effect of the EO on the biochemical behavior of the yeast Saccharomyces cerevisiae LMBF Y-16 was investigated. As the concentration of the EO increased, the more the exponential phase of the microbial growth decreased; furthermore, the biomass yield on the glucose consumed significantly decreased with the addition of the oil on the medium. The addition of the EO in small concentrations (e.g., 0.3 mL/L) did not present a remarkable negative effect on both the final biomass concentration and maximum ethanol quantity produced. In contrast, utilization of the extract in higher concentrations (e.g., 1.2 mL/L) noticeably inhibited microbial growth as the highest biomass concentration achieved, maximum ethanol production, and yield of ethanol produced per glucose consumed drastically declined. Concerning the composition of cellular lipids, the addition of the EO induced an increment in the concentration of cellular palmitic, stearic, and linoleic acids, with a concomitant decrease in the cellular palmitoleic acid and oleic acids.
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In the Mexican croplands(Biodegradationare generated largemodelingamountsof sludgeof agroindustrialbioreactors of wastestotal petroleumthat arehydrocarbonsusually not exploited.weathering Damagedin soil fruits wasted in the municipality of Tres Valles, Veracruz, are an excellent feedstock to produce ethanol, since do not need a and sediments) sophisticated pretreatment and have high fermentable sugar concentrations. In this work is described ethanol production from damaged fruits by a new strainS.A. Medina-Moreno,of SaccharomycesS. Huerta-Ochoa,cerevisiae isolatedC.A. Lucho-Constantino,from Agave sp. wastes.L. Aguilera-Vázquez,FermentationsA.wereJiménez-carried out in batch and repeated batch culturesGonzálezusingy M. biocatalystsGutiérrez-Rojasformed by S. cerevisiae AP1 cells immobilized into alginate-coated polyester fiberfill. Biocatalysts 259 showed Crecimiento, a high fermentative sobrevivencia capability y adaptación at de reducing Bifidobacterium sugar concentrations infantis a condiciones higher ácidas than 30 g L⁻¹. In batch cultures, with 32.58 g reducing sugar L⁻¹, was produced up to 15.39 g ethanol L⁻¹ at 16 h, with a volumetric productivity of 0.962 g L⁻¹ h⁻¹ and a fermentation(Growth, survivalefficiencyand ofadaptation94.77%.ofInsteadBifidobacteriumin a 5-cycleinfantisrepeatedto acidicbatchconditions)fermentation, with a reducing sugar content among 30 to 43 g L. L⁻¹Mayorga-Reyes,, ethanol production P. Bustamante-Camilo, in each cycle was A. fast, Gutiérrez-Nava, higher than E. 15 Barranco-Florido g L⁻¹, with fermentation y A. Azaola-efficiencies higher than 80%, and with volumetric productivities from 2.5 to 2.9 g L⁻¹ h⁻¹ after second cycle. Afterwards five cycles of repeated batch fermentation, Espinosa total ethanol production was 95.41 g L⁻¹ in just 44 h process. © 2023, Universidad Autonoma Metropolitana. All rights reserved.
... Glycerol is an effective and very competitive carbon source for SCO production compared to xylose [4]. Xylose is typically metabolized through the pentose-phosphate pathway that presents lower efficiency in terms of biomass and metabolite formation, compared to the EMP glycolysis that is used for the catabolism of glycerol or C6 sugars [12,27,32]. In the case of R. toruloides DSM 4444, several studies have demonstrated its enhanced potential to produce SCO in various fermentation substrates. ...
The potential of Rhodosporidium toruloides, Candida oleophila, Metschnikowia pulcherima, and Cryptococcus curvatus species to produce single-cell-oil (SCO) and other valuable metabolites on low-cost media, based on commercial-type xylose, was investigated. Rhodosporidium strains were further evaluated in shake-flasks using different lignosulphonate (LS) concentrations, in media mimicking waste streams derived from the paper and pulp industry. Increasing the LS concentration up to 40 g/L resulted in enhanced dry cell weight (DCW) while SCO production increased up to ~5.0 g/L when R. toruloides NRRL Y-27012 and DSM 4444 were employed. The intra-cellular polysaccharide production ranged from 0.9 to 2.3 g/L in all fermentations. Subsequent fed-batch bioreactor experiments with R. toruloides NRRL Y-27012 using 20 g/L of LS and xylose, led to SCO
production of 17.0 g/L with maximum lipids in DCW (YL/X) = 57.0% w/w. The fatty acid (FA)
profile in cellular lipids showed that oleic (50.3–63.4% w/w) and palmitic acid (23.9–31.0%) were the
major FAs. Only SCO from batch trials of R. toruloides strains contained α-linolenic acid. Media that
was supplemented with various LS concentrations enhanced the unsaturation profile of SCO from
R. toruloides NRRL Y-27012. SCO from R. toruloides strains could replace plant-based commodity oils
in oleochemical-operations and/or it could be micro- and nano-encapsulated into novel food-based
formulas offering healthier food-products.
