Sugar Utilization Research Articles

Sink Strength During Sugarcane Culm Growth: Size Matters

Sugarcane growth and its subsequent yield are linked to plant height. The increase in sugarcane height is controlled by elongation of the top 6 to 7 internodes. The elongation of the internodes can be significantly reduced by an application of the Trinexapac-ethyl (Moddus®) which is a known disruptor of GA synthesis. In this study, the growth and composition of the internodes were analysed following the treatment. We found that the strong inhibitory effect of Moddus® on internode size was due to a strongly suppressed rate of internode elongation, with no effect on the duration of the elongation period. The Moddus® inhibition of internode elongation was not due to a lack of an osmotic potential gradient but probably reflects a higher pressure potential of the tissue. A consequence of the reduced internode size was a significant reduction in carbon flow (sink strength) of the internode. It was not only the rate of internode growth that was altered by Moddus®, but also partitioning within the internode. Partitioning of carbon into components other than the soluble sugars and cell wall was significantly reduced by the Moddus® treatment. The high reducing sugar content in the Moddus® treatment suggests that sucrose mobilisation (hydrolysis by invertases and cleavage by sucrose synthase) might, like the duration of elongation, be controlled by thermal time. No accumulation of reducing sugars was evident in the control internodes probably due to the rapid mobilisation to other cellular processes. Sucrose accumulation in the internode reflected a cessation of sugar utilisation to support growth and maintenance.

Glyceraldehyde-3-phosphate dehydrogenase is required for fire blight disease establishment in apple fruitlets

Host sugar resource utilization is an essential aspect of parasitism by Erwinia amylovora, the bacterium that causes fire blight disease of pome fruits. We assessed the virulence of E. amylovora glyceraldehyde-3-phosphate dehydrogenase (gapA) mutants, which are predicted to be defective in sugar utilization through both glycolysis and the phosphogluconate pathway. A plasmid insertion mutant and an allelic exchange mutant of gapA were generated and found to be avirulent in apple fruitlets. The gapA insertion mutant was unstable, with insertion element excision resulting in restoration of pathogenicity. The results indicate that gapA is essential for E. amylovora virulence on apple fruitlets.

Recovery of carbon from rice straw for production of high-value products by Chlorella sorokiniana TH01 through mixotrophic cultivation

Rice straw is an abundant agricultural by-product in Viet Nam. Rice straw mainly contains carbohydrate (e.g., hemicellulose and cellulose), an abundant carbon source for biological production of high-value products, which is being used for animal feeding, burning or disposal in most suburban and rural areas of Viet Nam. The treatment of rice straw by burning and/or disposal has caused environmental pollution due to emission of greenhouse gases (e.g., CO2, CH4), toxic gases (CO, SOx, NOx) and dust. It is critical to apply technological measures replacing the traditional method to sustainably treat the huge volume of rice straw. In this study, rice straw carbohydrate was transformed to sugar-rich hydrolysate via a different chemical and enzymatic treatment methods for cultivation of Chlorella sorokiniana TH01 to produce lutein, lipid and protein. Data showed that the combined treatment of NaOH/H2SO4/Enzyme resulted in the maximal glucose and xylose hydrolysis efficiency of 96.32% and 93.43%, respectively. C. sorokiniana TH01 displayed the best growth in the hydrolysate with initial sugar concentration of 15 g/L diluted in BG-11 medium, achieving the maximal biomass concentration of 6.5 g/L (biomass yield of 0.44 g DCW/g substrate). Lutein, lipid, carbohydrate and protein contents were determined as 7.2, 350, 220 and 260 mg/g biomass, respectively. The sugar utilization efficiency by C. sorokiniana TH01 was determined as 94.67%. C. sorokiniana TH01 exhibited a promising capability in recovery of carbon from rice straw for production of high-value multiple commercial products, keeping rice straw in a circular economy and finally reaching a carbon-neutral process.

THE OBTAINING OF WATER-ALCOHOLIC AND SUGAR EXTRACTS FROM BERRIES

It was investigated the extraction of the dry substances with a water-alcohol solvent and the subsequent preparation of sugar extract from black currant, jostaberry, and plum. The water-alcohol solvent extracts the least dry matter from currant berries. The dry substance content in the black currant extract was 1.6%, while water-alcohol extracts from jostaberry and plum contained 4.3-5.5% of dry substances. At the same time, the content of dry substances in the extract is 1.6%, while water-alcohol extracts from gooseberry and plum contain 4.3–5.5% of dry substances. A significant amount of alcohol accumulates in the berries during the water-alcohol extraction. The alcohol content in all extracts, compared to the extractant, decreases from 40.0 to 25.06–26.39 wt. %. Simultaneously the alcohol losses decrease in further obtaining sugar extract from berries. The alcohol content in berries reaches 9.79 wt.% in black currant, 14.51 wt.% in plum, and 14.92 wt. % in jostaberry extract, particularly. The obtained sugar extracts contain different amounts of dry matter depending on the type of berries. The maximum degree of sugar utilization (79.0%) was during the preparation of black currant extract, which contains the maximum amount of dry substances (43.4%). The degree of sugar utilization by the plum extract obtaining was 71.6%. That corresponds to the dry substances content in the extract at 34.5%. The minimum degree of sugar utilization (31.5%) was during the production of jostaberry extract. The degree of sugar use ensures the content of dry substances in the extract of 31.8%. It was established that water-alcohol and sugar extracts from berries have maxima of visible light absorption in the range corresponding to anthocyanins absorption. The highest optical density has a water-alcohol extract from currants. A high content of polyphenolic compounds characterizes that. We established that acids are extracted almost the same amount from the berry raw material with a water-alcohol solution and during sugar treatment. The extracts from jostaberry have the maximum acidity, and its lowest value is characteristic of extracts from plum. The degree of extraction of vitamin C from berries was approximately the same and was 59% for jostaberry and 66% for black currant and plum. The perspective of using berries after extracting them as raw materials for obtaining various confectionery products is indicated.

Fast Dissolving Tablet

Fast dissolving tablets (FDTs) are a sort of oral strong measurement structure that crumbles or disintegrates rapidly in the oral cavity, bringing about fast medication retention and beginning of activity. These tablets have acquired fame because of their benefits over ordinary tablets, including simplicity of organization, expanded patient consistence, and further developed bioavailability .FDTs can be ready by different strategies, including direct pressure, freeze-drying, sublimation, splash drying, and hot-soften expulsion. They can be intended to deliver the medication quickly upon contact with spit or after a particular time delay, contingent upon the medication's physicochemical properties and restorative prerequisites. The definition of FDTs includes the utilization of different excipients, for example, super disintegrants , sugars, flavors, and oils, to work on the tablet's taste, mouthfeel, and crumbling time. The decision of excipients relies upon the medication's properties and the ideal disintegration profile. FDTs have tracked down applications in different remedial regions, including analgesics, antiemetics, allergy meds, and cardiovascular medications. They are especially valuable for drugs with a limited restorative window, where quick beginning of activity is basic, and for patients who experience issues gulping ordinary tablets. All in all, FDTs are a promising medication conveyance framework that gives a helpful, patient-accommodating, and compelling approach to managing drugs. With the rising interest for effective and simple to-regulate drug items, the FDT market is supposed to fill fundamentally before very long.

Purified cellulase-mediated simultaneous sugar utilization by Bacillus albus isolated from Similipal, Odisha, India.

Among 24 isolated cellulolytic bacteria from Similipal Biosphere Reserve, the most efficient isolate was recognized as a strain of Bacillus albus. This strain of B. albus was evaluated for cellulase production and the cellulase activity was measured in submerged fermentation using substrate carboxymethyl cellulose (CMC). Different nutritional (carbon, nitrogen, and metal-ion sources) and physical variables (pH, temperature, substrate concentration, and incubation time) during the growth of B. albus were optimized to obtain maximum cellulase activity. The highest cellulase activity of 5.79 U/mL for B. albus was observed at pH 6.75, temperature 37.5°C, CMC concentration 8.5 g/L, and 42 h incubation time. Further, supplementation of glucose as a subsidiary carbon source, yeast extract, peptone as nitrogen sources, and MgSO4 and MnSO4 as metal-ion sources enhance the cellulase activity of B. albus. The purified enzyme was reported to have a molecular weight of ∼54 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A zymogram analysis evidenced the cellulase activity of the purified enzyme fractions obtained from diethylaminoethyl cellulose chromatography. The purified cellulase was reported to have an optimum pH and temperature of 7.0°C and 50°C, respectively with a capacity of retaining its 60% residual activity within pH 6.0-8.0 and temperature 30-40°C, respectively. The metal ions, K+ and Na+ were the activators, while Pb2+ and Hg2+ were the inhibitors for the purified cellulase. The purified cellulase showed Km and Vmax values of 0.38 M and 8.19 U/mL, respectively, in presence of the substrate CMC and also simultaneous consumption of both hexose and pentose sugars.

Controlled Aeration Driven by Oxidation-Reduction Potential Affects Ester Profile in Wine Alcohol Fermentation with Different Starter Cultures

Background and Aims. Aeration, an important operation in winemaking, cannot be controlled accurately based on dissolved oxygen for ester production in wine alcohol fermentation. The following study describes an aeration control method with oxidation-reduction potential (ORP) in alcohol fermentation and investigates its effect on ester production in fermentations with different starter cultures. Methods and Results. The proposed method is based on using ORP as a switch for aeration timing. Different aeration levels driven by ORP were performed in wine alcohol fermentation with different starter cultures including Saccharomyces cerevisiae (Sc), Pichia fermentans (Pf), Hanseniaspora uvarum (Hu), and their mixes (Pf/Sc and Hu/Sc). The accumulated aeration volume, residual sugar concentration, viable cell number, and ester concentration were analyzed. Results showed that aeration levels could be controlled effectively with an ORP value, and aeration with higher ORPs triggered faster sugar utilization in Sc and Hu/Sc fermentation. Pf and Hu survived one day less in their respective cofermentation with aeration when ORP was −100 mV or −50 mV compared to the natural ORP (−150 mV∼−105 mV in Pf/Sc and −141 mV∼−107 mV in Hu/Sc, respectively). Aeration driven by ORP changed ester profiles in cofermentations. With the aeration levels increasing, the proportion of medium-chain fatty acid ethyl esters in the concentration of total esters first increased and then decreased in Hu/Sc fermentation. When ORP was −100 mV in Pf/Sc fermentation, the proportion of higher alcohol acetates to total esters was highest (8.14%), while that of ethyl acetate to total esters was lowest (87.35%). Conclusions. Aeration driven by ORP improved wine ester profiles by increasing the proportion of medium-chain fatty acid ethyl esters or reducing that of ethyl acetate in cofermentations. Significance of the Study. The present study will allow wineries and researchers to optimize the aeration process in alcohol fermentation and develop a scientific aeration strategy to improve the wine ester profile and aroma quality.

Sucrose-directed porous carbon interfaced α-Fe2O3-rGO for supercapacitors

Simultaneously embedding resonating 2D carbon into a metal oxide as a template and decorating in graphene layers offer a great strategy to enhance electronic properties in supercapacitor application. Brown sugar is abundant macromolecule with high content of sucrose and the application in supercapacitors would build diversification of brown sugar utilization. In this study, an interconnected network of iron oxide-mesoporous carbon hybrid (rGO/su-GC@Fe2O3) is synthesised through a microwave-assisted gel combustion using brown sugar as the carbon precursor to serve as Fe2O3 template, followed by wrapping the material within rGO nanosheets. Exploring the properties for supercapacitor, it delivered high specific capacitance of 1978F/g at 1 A/g and a cycling retention of 95.2% after consecutive 8000 cycles. The excellent performance hinges on the inimitable morphology with mesoporous channels marked with large surface area of 486 m2/g, high mesoporous percentage and the synergistic effect from resonating 2D graphitizable carbon, Fe2O3 and conductive rGO matrix. These results assert rGO/su-GC@Fe2O3 as productive promising supercapacitive electrode material for future utilization, meanwhile it could be applied in adsorption and electrocatalysis.

Optimization of food-fuel-fibre in biorefinery based on environmental and economic assessment: The case of sugarcane utilization in Thailand

Biomaterials utilization in biorefineries for food, fuel, and fibre is advantageous in terms of income and employment but may also have certain negative repercussions. This study focused on the optimum utilization of sugarcane-based products considering several sustainability indices, viz., greenhouse gas emissions, production costs, and profitability. The cane and sugar utilization in Thailand was optimized with the help of linear programming considering multiple scenarios, decision variables, and system constraints. Furthermore, the considered scenarios were ranked by following the Analytic Hierarchy Process. The scenario where the additional sugarcane was used for sugar production and the extra molasses was used for ethanol production received the highest ranking, followed by supplying extra bagasse to power plants. Nevertheless, the results showed that polylactic acid production, which has been highly promoted by the government, is still not attractive enough to persuade the industrial sector because of its high production cost. It is also interesting to note that direct ethanol production from excess sugarcane does not yield preferable results in terms of sustainability. The results showed that excess bagasse to power plant dominated the production cost and greenhouse gas emission while the extra sugar to PLA production and bagasse based-electricity could induce high profitability in the system. Based on the different weighting schemes, a sustainability triangle was developed to present the influence areas of the considered scenarios. The concept of a sustainability triangle would be beneficial for the decision-makers to choose the appropriate pathway by explicitly revealing the tradeoffs between the various sustainability aspects.

Profiling potential brewing yeast from forest and vineyard ecosystems

The brewing ability of wild yeast strains obtained from forest and vineyards ecosystems was analysed and compared with commercial yeast strains. The selection of new yeast strains as a way to create new beer aromas and flavours and to use local strains to promote the proximity ingredients in brewing is a topic of interest in the craft beer sector. Seventy-six wild Saccharomyces and non-Saccharomyces isolates and eighteen control strains were evaluated for their enzymatic activity and brewing capacity. The early screening system was set up to profile their enzymatic activity, utilisation of wort sugars and the effect of hop acids and ethanol on yeast growth. The microvolume screening method allows a large number of samples to be studied at the same time, permitting an affordable and rapid characterization in a relatively short period of time. Twenty-eight strains were selected using this method and tested in small-scale fermentations. Finally, three of these strains, all belonging to the species Lachancea thermotolerans, showed great potential and adaptability to ferment different wort styles, although further studies will be necessary to test their possibilities as beer starters. Understanding yeast enzymatic profiles and the influence of beer ingredients on their fermentation activity provides a platform to select strains for further consideration in brewing research.

In-situ detoxification and enhanced oxygen mass transfer for C5 sugar acid production from corncob hemicellulose hydrolysates using activated carbon particles

In this work, an easily implemented and cost-effective activated carbon (AC) enhanced technique was proposed for C5 sugar acid production from corncob hemicellulose hydrolysates. The optimum AC detoxification conditions were obtained by response surface methodology, and the fermentation kinetics behaviors were comparatively evaluated using two fermentation modes: separate detoxification and fermentation (SDF) and in-situ detoxification and fermentation (In-situDF). An investigation of the AC function demonstrates it offers synchronous detoxification and oxygen transfer enhancement, with a final increase of XA fermentation yield and productivity. This study shows a potential of detoxification and oxygen transfer enhancement in one-pot in C5 sugar acid production, which may smooth the way for commercial utilization of C5 sugars from lignocellulosic biomass in the future.

Climate warming has direct and indirect effects on microbes associated with carbon cycling in northern lakes.

Northern lakes disproportionately influence the global carbon cycle, and may do so more in the future depending on how their microbial communities respond to climate warming. Microbial communities can change because of the direct effects of climate warming on their metabolism and the indirect effects of climate warming on groundwater connectivity from thawing of surrounding permafrost, especially at lower landscape positions. Here we used shotgun metagenomics to compare the taxonomic and functional gene composition of sediment microbes in 19 peatland lakes across a 1600-km permafrost transect in boreal western Canada. We found microbes responded differently to the loss of regional permafrost cover than to increases in local groundwater connectivity. These results suggest that both the direct and indirect effects of climate warming, which were respectively associated with loss of permafrost and subsequent changes in groundwater connectivity interact to change microbial composition and function. Archaeal methanogens and genes involved in all major methanogenesis pathways were more abundant in warmer regions with less permafrost, but higher groundwater connectivity partly offset these effects. Bacterial community composition and methanotrophy genes did not vary with regional permafrost cover, and the latter changed similarly to methanogenesis with groundwater connectivity. Finally, we found an increase in sugar utilization genes in regions with less permafrost, which may further fuel methanogenesis. These results provide the microbial mechanism for observed increases in methane emissions associated with loss of permafrost cover in this region and suggest that future emissions will primarily be controlled by archaeal methanogens over methanotrophic bacteria as northern lakes warm. Our study more generally suggests that future predictions of aquatic carbon cycling will be improved by considering how climate warming exerts both direct effects associated with regional-scale permafrost thaw and indirect effects associated with local hydrology.

The protective effect of lactose on the bile salt stress response of Streptococcus thermophilus is strain dependent

Streptococcus thermophilus is generally considered to be sensitive to bile salt stimulation, and its bile salt tolerance is strain specific. In this study, the viable bacteria count, sugar utilization capacity, β-galactosidase activity, and extracellular polysaccharide synthesis capacity of 5 strains of Streptococcus thermophilus in bile salt with or without (w/o) lactose were measured to explore the protective ability of lactose to the strains. The changes in gene expression in stress and carbohydrate metabolism-related pathways were recorded. The results indicated that the protective effect of lactose on the bile salt stress response of Streptococcus thermophilus is strain dependent. The β-galactosidase activity of the strains was correlated with the yield of exopolysaccharides (EPS) significantly, and the strain with a high survival rate (4M6) showed higher lactose utilization, β-galactosidase activity and more EPS production in general.

Unique alcohol dehydrogenases involved in algal sugar utilization by marine bacteria

Marine algae produce complex polysaccharides, which can be degraded by marine heterotrophic bacteria utilizing carbohydrate-active enzymes. The red algal polysaccharide porphyran contains the methoxy sugar 6-O-methyl-d-galactose (G6Me). In the degradation of porphyran, oxidative demethylation of this monosaccharide towards d-galactose and formaldehyde occurs, which is catalyzed by a cytochrome P450 monooxygenase and its redox partners. In direct proximity to the genes encoding for the key enzymes of this oxidative demethylation, genes encoding for zinc-dependent alcohol dehydrogenases (ADHs) were identified, which seem to be conserved in porphyran utilizing marine Flavobacteriia. Considering the fact that dehydrogenases could play an auxiliary role in carbohydrate degradation, we aimed to elucidate the physiological role of these marine ADHs. Although our results reveal that the ADHs are not involved in formaldehyde detoxification, a knockout of the ADH gene causes a dramatic growth defect of Zobellia galactanivorans with G6Me as a substrate. This indicates that the ADH is required for G6Me utilization. Complete biochemical characterizations of the ADHs from Formosa agariphila KMM 3901T (FoADH) and Z. galactanivorans DsijT (ZoADH) were performed, and the substrate screening revealed that these enzymes preferentially convert aromatic aldehydes. Additionally, we elucidated the crystal structures of FoADH and ZoADH in complex with NAD+ and showed that the strict substrate specificity of these new auxiliary enzymes is based on a narrow active site.Key points• Knockout of the ADH-encoding gene revealed its role in 6-O-methyl-D-galactose utilization, suggesting a new auxiliary activity in marine carbohydrate degradation.• Complete enzyme characterization indicated no function in a subsequent reaction of the oxidative demethylation, such as formaldehyde detoxification.• These marine ADHs preferentially convert aromatic compounds, and their strict substrate specificity is based on a narrow active site.

Fermentative production of astaxanthin from sorghum distillery residue by an indigenous Aurantiochytrium sp. CJ6 strain using a continuous-feeding fed-batch process

In this study, Aurantiochytrium sp. CJ6 was cultivated heterotrophically on a waste resource, sorghum distillery residue (SDR) hydrolysate without adding any nitrogen sources. Mild sulfuric acid treatment released sugars that supported the growth of CJ6. Optimal operating parameters (salinity, 2.5%; pH, 7.5; with light exposure) determined using batch cultivation attained biomass concentration and astaxanthin content of 3.72 g/L and 69.32 µg/g dry cell weight (DCW), respectively. Using continuous-feeding fed-batch (CF-FB) fermentation, the biomass concentration of CJ6 increased to 6.3 g/L with biomass productivity and sugar utilization rate of 0.286 mg/L/d and 1.26 g/L/d, respectively. Meanwhile, CJ6 obtained maximum astaxanthin content (93.9 µg/g DCW) and astaxanthin concentration (0.565 mg/L) after 20-day cultivation. Thus, the CF-FB fermentation strategy seems to have a high potential for the cultivation of thraustochytrids to produce the high-value product (astaxanthin) using SDR as the feedstock to achieve circular economy.

Fermentation performance of oleaginous yeasts on Eucommia ulmoides Oliver hydrolysate: Impacts of the mixed strains fermentation

This present study mainly focused on the investigation and optimization of the fermentation performance of oleaginous yeasts on Eucommia ulmoides Oliver hydrolysate (EUOH), which contains abundant and diverse sugars. More importantly, the impacts of the mixed strains fermentation compared with the single strain fermentation were analyzed and evaluated, through systematic investigations of substrate metabolism, cell growth, polysaccharide and lipid production, COD and ammonia-nitrogen removals. It was found that the mixed strains fermentation could effectively promote a more comprehensive and thorough utilization of the various sugars in EUOH, greatly improve COD removal effect, biomass and yeast polysaccharide production, but could not significantly improve the overall lipid content and ammonia nitrogen removal effect. In this study, when the two strains with the highest lipid content (i.e. L. starkeyi and R. toruloides) were mixed-cultured, the maximum lipid yield of 3.82 g/L was achieved, and the yeast polysaccharide yield, COD and ammonia-nitrogen removal rates of the fermentation (LS+RT) were 1.64 g/L, 67.4% and 74.9% respectively. When the strain with the highest polysaccharide content (i.e. R. toruloides) was mixed-cultured with the strains with strong growth activity (i.e. T. cutaneum and T. dermatis), a large amount of yeast polysaccharides could be obtained, which were 2.33 g/L (RT+TC) and 2.38 g/L (RT+TD) respectively. And the lipid yield, COD and ammonia-nitrogen removal rates of the fermentation (RT+TC), (RT+TD) were 3.09 g/L, 77.7%, 81.4% and 2.54 g/L, 74.9%, 80.4%, respectively.

Draft Genome Sequence of Thermomicrobium sp. Strain 4228-Ro, a Thermophilic Bacterium Isolated from a Kamchatka Hot Spring.

The genome of Thermomicrobium sp. strain 4228-Ro, an aerobic thermophilic bacterium isolated from a Kamchatka hot spring, was sequenced and analyzed. The genome assembly comprises 13 contigs with a total length of 3,068,448 bp. Genome analysis revealed the pathway of aerobic utilization of sugars, which was corroborated by growth experiments.

Disrupting Central Carbon Metabolism Increases β-Lactam Antibiotic Susceptibility in Vibrio cholerae.

Antibiotic tolerance, the ability of bacteria to sustain viability in the presence of typically bactericidal antibiotics for extended time periods, is an understudied contributor to treatment failure. The Gram-negative pathogen Vibrio cholerae, the causative agent of cholera, becomes highly tolerant to β-lactam antibiotics (penicillin and related compounds) in a process requiring the two-component system VxrAB. VxrAB is induced by exposure to cell wall damaging conditions, which results in the differential regulation of >100 genes. While the effectors of VxrAB are relatively well known, VxrAB environment-sensing and activation mechanisms remain a mystery. Here, we used transposon mutagenesis to screen for mutants that spontaneously upregulate VxrAB signaling. This screen was answered by genes known to be required for proper cell envelope homeostasis, validating the approach. Unexpectedly, we also uncovered a new connection between central carbon metabolism and antibiotic tolerance in Vibrio cholerae. Inactivation of pgi (vc0374, coding for glucose-6-phosphate isomerase) resulted in an intracellular accumulation of glucose-6-phosphate and fructose-6-phosphate, concomitant with a marked cell envelope defect, resulting in VxrAB induction. Deletion of pgi also increased sensitivity to β-lactams and conferred a growth defect on salt-free LB, phenotypes that could be suppressed by deleting sugar uptake systems and by supplementing cell wall precursors in the growth medium. Our data suggest an important connection between central metabolism and cell envelope integrity and highlight a potential new target for developing novel antimicrobial agents. IMPORTANCE Antibiotic tolerance (the ability to survive exposure to antibiotics) is a stepping stone toward antibiotic resistance (the ability to grow in the presence of antibiotics), an increasingly common cause of antibiotic treatment failure. The mechanisms promoting tolerance are poorly understood. Here, we identified central carbon metabolism as a key contributor to antibiotic tolerance and resistance. A strain with a mutation in a sugar utilization pathway accumulates metabolites that likely shut down the synthesis of cell wall precursors, which weakens the cell wall and thus increases susceptibility to cell wall-active drugs. Our results illuminate the connection between central carbon metabolism and cell wall homeostasis in V. cholerae and suggest that interfering with metabolism may be a fruitful future strategy for the development of antibiotic adjuvants.

Direct liquid transmission of sound has little impact on fermentation performance in Saccharomyces cerevisiae.

Sound is a physical stimulus that has the potential to affect various growth parameters of microorganisms. However, the effects of audible sound on microbes reported in the literature are inconsistent. Most published studies involve transmitting sound from external speakers through air toward liquid cultures of the microorganisms. However, the density differential between air and liquid culture could greatly alter the sound characteristics to which the microorganisms are exposed. In this study we apply white noise sound in a highly controlled experimental system that we previously established for transmitting sound underwater directly into liquid cultures to examine the effects of two key sound parameters, frequency and intensity, on the fermentation performance of a commercial Saccharomyces cerevisiae ale yeast growing in a maltose minimal medium. We performed these experiments in an anechoic chamber to minimise extraneous sound, and find little consistent effect of either sound frequency or intensity on the growth rate, maltose consumption, or ethanol production of this yeast strain. These results, while in contrast to those reported in most published studies, are consistent with our previous study showing that direct underwater exposure to white noise sound has little impact on S. cerevisiae volatile production and sugar utilization in beer medium. Thus, our results suggest the possibility that reported microorganism responses to sound may be an artefact associated with applying sound to cultures externally via transmission through air.

A common inducer molecule enhances sugar utilization by Shewanella oneidensis MR-1.

Shewanella oneidensis MR-1 is an electroactive bacterium that is a promising host for bioelectrochemical technologies, which makes it a common target for genetic engineering, including gene deletions and expression of heterologous pathways. Expression of heterologous genes and gene knockdown via CRISPRi in S. oneidensis are both frequently induced by β-D-1-thiogalactopyranoside (IPTG), a commonly used inducer molecule across many model organisms. Here, we report and characterize an unexpected phenotype; IPTG enhances the growth of wild-type S. oneidensis MR-1 on the sugar substrate N-acetylglucosamine (NAG). IPTG improves the carrying capacity of S. oneidensis growing on NAG while the growth rate remains similar to cultures without the inducer. Extracellular acetate accumulates faster and to a higher concentration in cultures without IPTG than those with it. IPTG appears to improve acetate metabolism, which combats the negative effect that acetate accumulation has on the growth of S. oneidensis with NAG. We recommend using extensive experimental controls and careful data interpretation when using both NAG and IPTG in S. oneidensis cultures.