Sugar Utilization Research Articles

Insights into β-manno-oligosaccharide uptake and metabolism in Bifidobacterium adolescentis DSMZ 20083 from whole-genome microarray analysis

Metabolism of non-digestible dietary glycans directly influences the structure and composition of human gut microbiota and, in turn, the host health. β-Mannans form an integral component of the modern diet as naturally occurring dietary fibre or additives in processed foods. In the present study, in vitro fermentation and TLC studies were used to determine the ability of adult-associated Bifidobacterium adolescentis DSMZ 20083 to utilise β-manno-oligosaccharides from guar gum, locust bean gum, konjac root, and copra meal generated using GH26 endo-β-mannanase (ManB-1601). Further, to gain insights into the underlying molecular mechanism, a whole-genome microarray analysis, RT-qPCR, and molecular docking studies were employed to reconstruct the copra meal β-manno-oligosaccharides (CM-β-MOS) utilisation pathway in B. adolescentis DSMZ 20083. B. adolescentis DSMZ 20083 grew appreciably (O.D600 nm up to 0.8) on all tested β-manno-oligosaccharides but maximally on CM-β-MOS. CM-β-MOS having DP2–3 were found to deplete from the fermentation media. Whole-genome transcriptome analysis, RT-qPCR, and molecular docking studies suggested that in B. adolescentis DSMZ 20083, ABC & MFS transporters are possibly involved in the uptake of DP ≥ 2 and DP ≥ 3 linear CM-β-MOS, respectively, while GH1 β-glucosidase, and GH32 β-fructofuranosidase possibly cleave linear CM-β-MOS into monosaccharides. Sugar absorption and utilisation pathways; Bifid shunt, ABC transport system, pyruvate metabolism, glycolysis/gluconeogenesis, pentose, and glucouronate inter-conversions were also found up-regulated following the growth on CM-β-MOS. This is the first study reporting on possible molecular determinants used by B. adolescentis DSMZ 20083 to utilise β-manno-oligosaccharides. Our studies can prove resourceful to food and nutraceutical industries, aiming at precision microbiome modulation using β-manno-oligosaccharides.

Effects of Xylanase Supplementation on the Performance, Nutrient Digestibility, and Digestive Organ Profiles of Broiler Chickens: A Meta-analysis

Enzymes supplementation in broiler feeding is commonly applied to optimize animal feed utilization and reduce feed production costs. One of the enzymes widely used in the broiler industry is xylanase which breaks down complex fibrous compounds in feed, such as nonstarch polysaccharides, to simpler utilizable sugar molecules. However, the effects of xylanase enzymes on broiler growth performance, nutrient digestibility, and organ function in broiler chickens were variable and inconclusive. Therefore, the current study aimed to evaluate the effect of the xylanase enzyme in feed on the performance, nutrient digestibility, and digestive function of parrots using a meta-analysis approach. A dataset of 140 points obtained from 53 articles was analyzed using a mixed model methodology. The results showed that the xylanase enzyme supplementation increased the broiler’s body weight gain and decreased feed consumption and feed conversion ratio. In addition, xylanase supplementation also increased nutrient digestibility, such as dry matter, crude protein, starch, gross energy, fat, phosphorus, and calcium. Concerning broiler organ weights, the xylanase supplementation in broiler feed significantly reduced the weight of the duodenum, small intestine, and relative length of the duodenum, jejunum, and ileum. Xylanase supplementation also tended to reduce the relative weight of the proventriculus. The results also showed a negative response to the crypt depth ileum of broiler due to xylanase supplementation. It can be concluded that xylanase supplementation improves the performance, nutrient digestibility, and digestive function of broiler chickens.

Dimethyl phthalate inhibits the growth of Escherichia coli K-12 by regulating sugar transport and energy metabolism.

Dimethyl phthalate (DMP) is one of the most widely used plasticizers, and it is easily released into the environment, posing a threat to microbes. In this study, the impact of DMP on the uptake and metabolism of sugars in E. coli K-12 was assessed using proteomics, computational simulation analysis, transcriptome analysis, and sugar utilization experiments. DMP contamination inhibited the growth of E. coli K-12 and downregulated the expression of proteins in ATP-binding cassette (ABC) transporters and the phosphotransferase (PTS) system of E. coli K-12, which are primarily involved in the transmembrane transport of sugars. DMP formed a stable complex with sugar transporters and changed the rigidity and stability of the proteins. Furthermore, DMP treatment decreased the utilization of L-arabinose, glucose, D-xylose, and maltose. Moreover, carbon metabolism and oxidative phosphorylation were also downregulated by DMP. Our study shows that DMP reduces the uptake of sugars and ATP production and subsequently inhibits the growth of E. coli K-12.

Methane Production by Facultative Anaerobic Wood-Rot Fungi via a New Halomethane-Dependent Pathway.

ABSTRACTThe greenhouse gas methane (CH4) is of pivotal importance for Earth’s climate system and as a human energy source. A significant fraction of this CH4 is produced by anaerobic Archaea. Here, we describe the first CH4 production by facultative anaerobic wood-rot fungi during growth on hydroxylated/carboxylated aromatic compounds, including lignin and lignite. The amount of CH4 produced by fungi is positively correlated with the amount of CH3Cl produced during the rapid growth period of the fungus. Biochemical, genetic, and stable isotopic tracer analyses reveal the existence of a novel halomethane-dependent fungal CH4 production pathway during the degradation of phenol and benzoic acid monomers and polymers and utilization of cyclic sugars. Even though this halomethane-dependent pathway may only play a side role in anaerobic fungal activity, it could represent a globally significant, previously overlooked source of biogenic CH4 in natural ecosystems.IMPORTANCE Here, we demonstrate that wood-rot fungi produce methane anaerobically without the involvement of methanogenic archaea via a new, halomethane-dependent pathway. These findings of an anaerobic fungal methane formation pathway open another avenue in methane research and will further assist with current efforts in the identification of the processes involved and their ecological implications.

Highly Efficient Utilization of Sugar in Molasses for Butyric Acid Production by Clostridium tyrobutyricum

Highly Efficient Utilization of Sugar in Molasses for Butyric Acid Production by Clostridium tyrobutyricum

Towards efficient production of highly optically pure d-lactic acid from lignocellulosic hydrolysates using newly isolated lactic acid bacteria

This study presents the production of D-lactic acid with high enantiomeric purity using lignocellulosic hydrolysates from newly isolated lactic acid bacterial (LAB) strains. Six strains, 4 heterofermentative and 2 homofermentative, were investigated for their ability to grow and produce lactic acid on sugar beet pulp (SBP) hydrolysates, containing a mixture of hexose and pentose sugars. Among the strains tested, three were isolates designated as A250, A257 and A15, all of which belonged to the genus Leuconostoc. Only strain A250 could be reliably identified as Leuconostoc pseudomesenteroides based on cluster analysis of Maldi-ToF spectra. All strains produced D-lactic acid in the presence of SBP hydrolysates, but with varying optical purities. The homofermentative strains achieved higher D-lactic acid optical purities, but without assimilating the pentose sugars. Co-cultivation of the homofermentative strain Lactobacillus coryniformis subsp. torquens DSM 20005 together with the heterofermentative isolate A250 led to the production of 21.7 g/L D-lactic acid with 99.3 % optical purity. This strategy enabled the complete sugar utilization of the substrate. Nanofiltration of the SBP hydrolysate enhanced the enantiomeric purity of the D-lactic acid produced from the isolates A250 and A15 by about 5 %. The highest D-lactic acid concentration (40 g/L) was achieved in fed-batch cultures of A250 isolate with nanofiltered SBP, where optical purity was 99.4 %. The results of this study underline the feasibility of a novel isolate as an efficient D-lactic acid producer using lignocellulosic hydrolysates.

Degradation‐induced microbiome alterations may aggravate soil nutrient loss in subalpine meadows

AbstractGrassland degradation has become a serious environmental problem worldwide. However, the link between grassland degradation and soil functional microorganisms remains unclear. Here, we investigated the effects of subalpine meadow degradation on the taxonomic and functional communities of the soil microbiome on Mount Wutai on the eastern margin of the Loess Plateau, China, using shotgun metagenomic sequencing. The results showed that vegetation degradation decreased most soil nutrients (e.g., soil organic carbon [SOC, −48.9%], total nitrogen [TN, −15.2%] and carbon [TC, −38.3%]), leading to significant changes in the taxonomic (r = 0.892, p < 0.001) and functional compositions (r = 0.972, p < 0.001) of the microbial communities (explaining 66.6% and 64.5% of the variance, respectively). The structural equation model (SEM) showed that variations in the soil nutrient status and plant parameters caused by degradation resulted in changes in the microbial community structure and function. The variations in the plant and microbial communities during degradation altered carbon (C) and nitrogen (N) cycling separately or interactively. Among the C degradation‐related genes, the relative abundances of cellulose degradation, sugar utilization and chitin degradation genes in moderately degraded (MD) and heavily degraded (HD) meadows were significantly higher than those in nondegraded (ND) meadows (p < 0.05). The abundance of denitrification genes (nirK, nirS, norB and norC) and nitrification genes (pmoA/amoA, pmoB/amoB, pmoC/amoC and hao) was higher in all degraded meadows, which increased the risk of soil N loss. Our findings revealed the negative feedback of microbes due to subalpine meadow degradation, during which metabolically active microbes tended to accelerate soil nutrient loss.

Physiological Factors Limiting Leaf Net Photosynthetic Rate in C3 Crops like Rice and Approaches for Improving It

Improving leaf photosynthetic capacity is one of the most promising approaches to further boost crop yield. Clarifying factors limiting leaf photosynthetic capacity, especially in C3 crops, is meaningful for designing strategies to improve it. Leaf net photosynthetic rate (A) is one of the parameters describing leaf photosynthetic capacity. In the present study, physiological factors limiting A in C3 crops such as rice were discussed and different approaches for A improvement were summarized to provide theoretical guidance for increasing leaf photosynthetic capacity. A will be limited by both CO2 availability and light intensity over periods from a few hours to several days, and by one of them over shorter intervals. Under current ambient atmospheric conditions, A of C3 crops is mainly limited by Rubisco activity and the CO2 concentration in chloroplasts. Leaf nitrogen content affects A by regulating Rubisco content and leaf anatomy; leaf morphological and anatomical traits limit A by impacting stomatal and mesophyll CO2 diffusion. Further improvements of A in C3 crops can be achieved by designing or introducing high-activity Rubisco; adjusting leaf nitrogen allocation to optimize leaf anatomy and leaf chemical composition; modifying leaf morphology and anatomy for greater CO2 diffusion; improving the activity of proteins and enzymes associated with sugar transportation and utilization; introducing C4 photosynthetic mechanisms and combining high photosynthetic traits by conventional breeding.

Experimental Evidence for Seed Metabolic Allometry in Barrel Medic (Medicago truncatula Gaertn.).

Seed size is often considered to be an important trait for seed quality, i.e., vigour and germination performance. It is believed that seed size reflects the quantity of reserve material and thus the C and N sources available for post-germinative processes. However, mechanisms linking seed size and quality are poorly documented. In particular, specific metabolic changes when seed size varies are not well-known. To gain insight into this aspect, we examined seed size and composition across different accessions of barrel medic (Medicago truncatula Gaertn.) from the genetic core collection. We conducted multi-elemental analyses and isotope measurements, as well as exact mass GC–MS metabolomics. There was a systematic increase in N content (+0.17% N mg−1) and a decrease in H content (–0.14% H mg−1) with seed size, reflecting lower lipid and higher S-poor protein quantity. There was also a decrease in 2H natural abundance (δ2H), due to the lower prevalence of 2H-enriched lipid hydrogen atoms that underwent isotopic exchange with water during seed development. Metabolomics showed that seed size correlates with free amino acid and hexoses content, and anticorrelates with amino acid degradation products, disaccharides, malic acid and free fatty acids. All accessions followed the same trend, with insignificant differences in metabolic properties between them. Our results show that there is no general, proportional increase in metabolite pools with seed size. Seed size appears to be determined by metabolic balance (between sugar and amino acid degradation vs. utilisation for storage), which is in turn likely determined by phloem source metabolite delivery during seed development.

A novel fermentation strategy for efficient xylose utilization and microbial lipid production in lignocellulosic hydrolysate

The sugar utilization efficiency and the tolerance of microorganism to inhibitors are essential for lipid production from lignocellulosic biomass. In this study, the sugar consumption and inhibitor tolerance characteristics of Trichosporon dermatis 32,903 were investigated. The results showed that the lipid yield on xylose was much lower than that on glucose, while these substrates exhibited comparative efficiency for cell growth. High inoculum size improved the tolerance of T. dermatis 32,903 to inhibitors. Based on these characteristics, sugar-targeted-utilization and cyclic fermentation strategy was developed. The tolerance of high inoculum size to inhibitors was utilized, glucose was targeted for lipid fermentation and xylose was targeted for cell growth. As a result, the lipid production efficiency was greatly enhanced. The lipid titer in hydrolysate of DLCA (Densifying Lignocellulosic biomass with Chemicals followed by Autoclave) pretreated rice straw was improved to as high as 38.4 g/L with lipid yield of 0.207 g/g consumed sugar.

Antifungal Effect of Henna (Lawsonia inermis) Extract on Pathogenic Fungi

The study aimed at undertaking preliminary phytochemical studies and antifungal activities of Lawsonia inermis leaf extracts against clinical Candida isolates from female patients attending Dalhatu Araf Specialist Hospital (DASH) Lafia, Nasarawa State. HVS (High Vaginal Swab) samples were collected from 185 subjects and transported to the laboratory for analysis. Microbial culture and isolations were done on Sabouraud dextrose agar (SDA), Blood agar, Potato dextrose agar (PDA) and Sabouraud dextrose broth. Identification of clinical isolates was done following standard guideline for Candida identification including microscopic, cultural and biochemical characteristics (sugar utilization and fermentation). Antifungal susceptibility tests of the plant extracts at different concentrations were carried out against Candida isolates. Distilled water and ketoconazole drug served as negative and positive control respectively. Zones of inhibitions, the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) of the extracts were determined. Data were analysed on the Minitab 16.0 software for descriptive (mean with standard error) and inferential statistics and Chi Square at 95% confidence limit. In conclusion, L.inermis leaf has been shown to have antifungal properties since it contained quality phytochemicals in sufficient quantity that may be explored in the synthesis of drugs against some species of Candida. This finding is crucial in the management and control of candidiasis in the study.

Using fluorescent promoter-reporters to study sugar utilization control in Bifidobacterium longum NCC 2705

Bifidobacteria are amongst the first bacteria to colonize the human gastro-intestinal system and have been proposed to play a crucial role in the development of the infant gut since their absence is correlated to the development of diseases later in life. Bifidobacteria have the capacity to metabolize a diverse range of (complex) carbohydrates, reflecting their adaptation to the lower gastro-intestinal tract. Detailed understanding of carbohydrate metabolism regulation in this genus is of prime importance and availability of additional genetic tools easing such studies would be beneficial. To develop a fluorescent protein-based reporter system that can be used in B. longum NCC 2705, we first selected the most promising fluorescent protein out of the seven we tested (i.e., mCherry). This reporter protein was then used to study the carbohydrate mediated activation of PBl1518 and PBl1694, two promoters respectively predicted to be controlled by the transcriptional factors AraQ and AraU, previously suggested to regulate arabinose utilization and proposed to also act as global transcriptional regulators in bifidobacteria. We confirmed that in B. longum NCC 2705 the AraQ controlled promoter (PBl1518) is induced strongly by arabinose and established that the AraU controlled promoter (PBl1694) was mostly induced by the hexoses galactose and fructose. Combining the mCherry reporter system with flow cytometry, we established that NCC 2705 is able to co-metabolize arabinose and glucose while galactose was only consumed after glucose exhaustion, thus illustrating the complexity of different carbohydrate consumption patterns and their specific regulation in this strain.

Temporal transcriptome analysis provides molecular insights into flower development in red-flesh pitaya

BackgroundPitaya is an important economic fruit worldwide due to its numerous health benefits. A systematic understanding of the mechanism underlying flower development is essential to obtain higher fruit yield and quality. However, the genetic mechanism of flower development is not yet investigated in pitaya. Herein, a transcriptome analysis was performed to determine the transcriptional changes during flower development in red-flesh pitaya by utilizing nine different stages of flower development. ResultA total of 95,412 unigenes were generated with a mean length of 913 nt, and N50 value of 1878 nt. Comparative transcriptomic analysis showed many differentially expressed genes (DEGs) among the flower growth stages. Furthermore, an array of key DEGs were enriched in hormone signaling, transcription, carbohydrate transport, and energy production pathways. In particular, indole-3-acetic acid, abscisic acid, ethylene-responsive transcription factor, constans-like, teosinte branched 1/cycloidea/proliferating cell nuclear antigen factor, apetala1-like, agamous-like MADS-box protein, sepallata, growth-regulating factor, putative axial regulator yabby, leafy/floricaula homolog, and MYB gene-associated transcription factors displayed altered expression, suggesting their critical roles in floral organ development of pitaya. Besides, genes related to sugar synthesis, transportation, and utilization mediate flower growth regulation in pitaya. Eleven genes were selected to perform qRT-PCR analysis to verify the results of the RNA sequencing. ConclusionsOur results provide important insights into the transcriptional regulation of pitaya flower development. These data resources will be a cornerstone for future research that aims at exploring the genetic control of flower development in pitaya.How to cite: Wu Z, Huang L, Huang F, et al. Temporal transcriptome analysis provides molecular insights into flower development in red-flesh pitaya. Electron J Biotechnol 2022;58 https://doi.org/10.1016/j.ejbt.2022.05.005

Malnutrition is Associated With Altered Gut Microbial Functions in 13-Year-Old Brazilian Children

ObjectivesUnder- and over-nutrition are increasingly present in low- and middle-income settings, leading to a double burden of malnutrition at a population or individual level. The gut microbiota may affect host's health via dietary component degradation for energy provision and maintenance of a homeostatic gut environment. This relationship may reshape during adolescence, corresponding to the last step of gut microbiota maturation, yet remains under-investigated. The objective of the work was to assess if gut microbial functions vary with body mass index-for-age and height-for-age z-scores (BMIZ, HAZ) in adolescents and if they are influenced by sex and pubertal stage.Methods340 13-year-old children (53% males) with no antibiotic use within the last 6 weeks from the 2004 Pelotas Birth Cohort, Brazil, were stratified using WHO cutoffs for BMIZ (wasting (n = 11); normal (n = 251); overweight/obese (n = 78)) and HAZ (stunting (n = 10); normal (n = 330)). Tanner staging was used to assess pubertal development (1 (n = 12); 2–4 (n = 212); 5 (n = 116)). Fecal microbiota was assessed via Illumina MiSeq (16S rRNA gene sequencing) and functions were inferred with PICRUSt2 and MetaCyc. Data were analyzed via DESeq2 in R.Results340 pathways were identified and 19 were differently represented (q-value < .05) according to BMIZ but not HAZ. Between overweight/obese and normal, these included 16 pathways important for energy metabolism and production of various metabolites such as Preq0; sex and pubertal stage accounted for differential representation of 8 of them. Using the wasting category as a comparator, 4 pathways related to vitamin B12 synthesis/salvage (accounted for by sex and pubertal stage) and sugars utilization were differentially represented in normal and overweight/obese categories.ConclusionsThese findings suggest that the functional potential of the adolescent gut microbiota is altered with BMIZ and may be a target, with sex and pubertal stage consideration, for interventions aimed at sustaining adolescent health.Funding SourcesJoannah and Brian Lawson Centre for Child Nutrition, University of Toronto, Canada, CONACyT scholarship, Wellcome Trust, World Health Organization, National Support Program for Centers of Excellence, Brazilian National Research Council, Brazilian Ministry of Health, Children's Pastorate.

Connecting Algal Polysaccharide Degradation to Formaldehyde Detoxification.

Formaldehyde is a toxic metabolite that is formed in large quantities during bacterial utilization of the methoxy sugar 6‐O‐methyl‐d‐galactose, an abundant monosaccharide in the red algal polysaccharide porphyran. Marine bacteria capable of metabolizing porphyran must therefore possess suitable detoxification systems for formaldehyde. We demonstrate here that detoxification of formaldehyde in the marine Flavobacterium Zobellia galactanivorans proceeds via the ribulose monophosphate pathway. Simultaneously, we show that the genes encoding the key enzymes of this pathway are important for maintaining high formaldehyde resistance. Additionally, these genes are upregulated in the presence of porphyran, allowing us to connect porphyran degradation to the detoxification of formed formaldehyde.

Dynamics of Changes in pH and the Contents of Free Sugars, Organic Acids and LAB in Button Mushrooms during Controlled Lactic Fermentation.

The aim of the study was to assess changes in the basic quality parameters induced by controlled lactic fermentation of fruiting bodies of the button mushroom (Agaricus bisporus). Lactiplantibacillus plantarum 299v with documented probiotic properties and L. plantarum EK3, i.e., an isolate obtained from spontaneously fermented button mushrooms, were used as starter strains. The fruiting bodies of fresh, blanched, and fermented mushrooms were analyzed at different stages of the lactic fermentation process. The content of free sugars (high-performance liquid chromatography with charged aerosol detector method; HPLC-CAD) and organic acids (high-performance liquid chromatography with diode array detector method; HPLC-DAD) was determined both in the mushroom fruiting bodies and in the brine. Five free sugars (ribose, trehalose, sucrose, glucose, and fructose), mannitol, and six organic acids (lactic, malic, succinic, citric, acetic, and fumaric acids) were detected in the samples. Lactic acid dominated in the final products. The starter cultures exhibited varying degrees of utilization of available mushroom sugars and sucrose used as an additional substrate. Sucrose was utilized at a higher rate and in greater amounts by the L. plantarum EK3 isolate. This starter culture was characterized by a significantly higher final amount of produced lactic acid, a lower pH value, and higher numbers of LAB (lactic acid bacteria). These important quality parameters largely determine the stability of fermented products. Based on the analysis results and the high scores in the organoleptic evaluation of the fermented mushrooms, the L. plantarum EK3 isolate can be recommended as an appropriate starter culture for lactic fermentation of mushroom fruiting bodies.

Dark-fermentative hydrogen production from synthetic lignocellulose hydrolysate by a mixed bacterial culture: The relationship between hydraulic retention time and pH conditions

This study assessed the effect of hydraulic retention time (HRT) ranging from 24 to 3 h on continuous dark-fermentative H2 production in four bioreactors operated at pH 5.0, 5.5, 6.0 and 6.5. A mixture of cellobiose, xylose and arabinose was used as the substrate. The highest hydrogen production rate between HRTs of 24 and 12 h was observed at pH 6.5, while at HRT below 12 h at pH 6.0. At a HRT of 3 h it reached 11.4 L H2/L-d. Thus, the optimum pH for H2 production depends on the HRT. The highest sugar utilization was obtained at pH 6.0 and 6.5 and decreased in the following order: cellobiose > xylose > arabinose. The pH conditions, in contrast to HRT, were found to have a significant influence on the bacterial composition. Low diversity in bacterial culture dominated by the Clostridium genus allows for stable and high H2 production performance.

Bifunctional alcohol/aldehyde dehydrogenase AdhE controls phospho-transferase system sugar utilization and virulence gene expression by interacting PtsH in Edwardsiella piscicida

The bifunctional alcohol/aldehyde dehydrogenase (AdhE), one of the key enzymes in the bacterial ethanol anaerobic fermentation pathway, is critical for appropriate expression of the genes for the utilization of carbon sources. Knowledge about its global roles in modulating gene expression and metabolomics remains limited. Edwardsiella bacteria includes several important zoonotic pathogenic species including Edwardsiella piscicida, a leading fish pathogen that causes severe economic losses in the aquaculture industry. It is well known to utilize few sugars. In this study, we showed that AdhE is involved in various processes including sugar utilization, bacteria growth, intracellular pH homeostasis, type III/VI secretion system (T3/T6SS) production, and survival in fish. Moreover, our unbiased metabolomics approaches revealed that AdhE modulates a large quantity of metabolic pathways, including amino acids, tricarboxylic acid (TCA) intermediates, sugar and fatty acids. Pull-down and Co-immunoprecipitation (IP) analysis revealed that AdhE interacts with the phospho-transferase system component PtsH that supports the transform of its PTS sugars including mannose to mannose-6P, the established metabolic ligand modulating EvrA activity to control T3/T6SS expression. Collectively, AdhE appears to play important roles in bacterial adapting to the internal environment changes by regulating sugar metabolic pathways and bacterial virulence expression. These observations support a model in which AdhE acts a macromolecule hub accommodating proteins to modulate the PTS and other signaling cascades related to pathogenesis and environmental adaptation in bacterial pathogens, which may provide new perspectives for attempts to attenuate bacterial virulence.

Detoxification of lignocellulosic prehydrolyzate by lignin nanoparticles prepared from biorefinery biowaste to improve the ethanol production.

This study proposed a recyclable p-toluenesulfonic acid (p-TsOH) fractionation process for co-producing lignin nanoparticles (LNPs) and fermentable sugars from lignocellulosic biorefinery biowaste (enzymatic hydrolysis residue (EHR)). The prepared LNPs were used to detoxify the inhibitors in the xylose-rich prehydrolyzate for improving ethanol production. Results showed that the EHR was fractionated into a cellulose-rich water-insoluble solid (WIS) fraction and a lignin-rich spent liquor (SL) fraction. Cellulase hydrolysis of WIS produced 97.7% of glucose yield, while the LNPs of an average particle size of 98.0 nm with 76.3 % yield (based on the untreated EHR) were obtained from the diluted SL. LNPs demonstrated higher detoxification ability than EHR at the same dosage. Moreover, the fermentability of the detoxified xylose-rich prehydrolyzate was significantly improved. The sugar utilization ratio was 94.8%, and the ethanol yield reached its peak value of 85.4% after 36 h of fermenting the detoxified xylose-rich prehydrolyzate.

GAL Regulon in the Yeast S. cerevisiae is Highly Evolvable via Acquisition in the Coding Regions of the Regulatory Elements of the Network.

GAL network in the yeast S. cerevisiae is one of the most well-characterized regulatory network. Expression of GAL genes is contingent on exposure to galactose, and an appropriate combination of the alleles of the regulatory genes GAL3, GAL1, GAL80, and GAL4. The presence of multiple regulators in the GAL network makes it unique, as compared to the many sugar utilization networks studied in bacteria. For example, utilization of lactose is controlled by a single regulator LacI, in E. coli’s lac operon. Moreover, recent work has demonstrated that multiple alleles of these regulatory proteins are present in yeast isolated from ecological niches. In this work, we develop a mathematical model, and demonstrate via deterministic and stochastic runs of the model, that behavior/gene expression patterns of the cells (at a population level, and at a single-cell resolution) can be modulated by altering the binding affinities between the regulatory proteins. This adaptability is likely the key to explaining the multiple GAL regulatory alleles discovered in ecological isolates in recent years.