Mixed Sugars Research Articles

Two-stage process production of microbial lipid by co-fermentation of glucose and N-acetylglucosamine from food wastes with Cryptococcus curvatus

Microbial lipids were produced through a two-stage process with Cryptococcus curvatus by co-fermenting rice and shrimp shells hydrolysates. In the first stage, biomass production of glucose and N-acetylglucosamine was optimized by response surface methodology with the maximum biomass yield (17.60 g/L) under optimum conditions (43.2 g/L mixed sugar concentration, pH 5.8, 200 rpm, and 28 °C). In the second stage, according to a single-factor optimization setting (43.2 g/L sugar mixture solutions, pH 5.5, and shift time of 36 h), lipid titer of 10.08 g/L with content of 55.30 % was achieved. Scaling up to a 5-L bioreactor increased lipid content to 60.07 % with 0.233 g/g yield. When Cryptococcus curvatus was cultured in the blends of rice hydrolysates and shrimp shells hydrolysate, lipid content and yield were 52.25 % and 0.204 g/g. The fatty acid compositions of lipid were similar to those of typical vegetable oils.

The potential of Burkholderia thailandensis E264 for co-valorization of C5 and C6 sugars into multiple value-added bio-products

Despite known metabolic versatility of Burkholderia spp., sugar metabolism and end-product synthesis patterns in Burkholderia thailandensis have been poorly characterized. This work has demonstrated that B. thailandensis is capable of simultaneously uptaking glucose and xylose and accumulating up to 64% of its dry mass as poly(3-hydroxyalkanoate) (PHA) biopolymers, resulting in a PHA titer of up to 3.8 g L−1 in shake flasks. Rhamnolipids – mainly (68–75%) in the form of Rha-Rha-C14-C14 – were produced concomitantly with a titer typically in the range of 0.2–0.4 g L−1. Gluconic and xylonic acids were also detected in titers of up to 5.3 g L−1, and while gluconic acid appeared to be back consumed, xylonic acid formed as a major end product. This first example of co-production of three products from mixed sugars using B. thailandensis paves the way for improving biorefinery economics.

Au-NP-based colorimetric assay for sugar detection and quantification

Sugars have been associated with health problems such as metabolic syndrome, obesity, elevated triglycerides, and other features of metabolic disorders. Here, we report on the design and characterization of a highly sensitive gold nanoparticle (AuNP)-based assay for measuring sugars levels in fluids. AuNPs are functionalized with 4-mercaptobenzoic acid (4MBA) to modulate surface plasmonic resonance (SPR) frequency and fluorescent energy absorption by AuNPs, based on a fixed concentration of fluorescein introduced along with a fluid sample containing a determined quantity of sugar. We find the driving mechanism to be kinetic competition between fluorescein and saccharide which occupies the active carboxylic sites of the functional groups on the nanoparticle surface. This drives a colorimetric response in the 4MBA-AuNP solution, from orange to green, discernible to the naked eye. The aggregation of functionalized AuNPs as a result of increasing sugar concentration was confirmed via UV–vis spectroscopy and identified by a spectral peak of 620–675 nm. The limit of detection (LOD) was (55.8 ± 1.1) µM, with a highly repeatable calibration curve in the range of 0.09 – 2.45 mM. The assay's cost-effectiveness, speed, and simplicity open the door to multiple applications associated with detecting and quantifying sugars, including food science. The sensory platform was successfully tested in mixed sugar solutions to study the sensitivity capacity and applied to strawberry and kiwi freeze-dried samples. The results are validated by HPLC with refractive index detection.

Precise prediction of metabolites patterns using machine learning approaches in distinguishing honey and sugar diets fed to mice

As a natural sweetener produced by honey bees, honey was recognized as being healthier for consumption than table sugar. Our previous study also indicated thatmetaboliteprofiles in mice fed honey and mixedsugardiets aredifferent. However, it is still noteworthy about the batch-to-batch consistency of the metabolic differences between two diet types. Here, the machine learning (ML) algorithms were applied to complement and calibrate HPLC-QTOF/MS-based untargeted metabolomics data. Data were generated from three batches of mice that had the same treatment, which can further mine the metabolite biomarkers. Random Forest and Extra-Trees models could better discriminate between honey and mixed sugar dietary patterns under five-fold cross-validation. Finally, SHapley Additive exPlanations tool identified phosphatidylethanolamine and phosphatidylcholine as reliable metabolic biomarkers to discriminate the honey diet from the mixed sugar diet. This study provides us new ideas for metabolomic analysis of larger data sets.

The novel properties of Kluyveromyces marxianus glucose sensor/receptor repressor pathway and the construction of glucose repression-released strains

BackgroundGlucose repression in yeast leads to the sequential or diauxic utilization of mixed sugars and reduces the co-utilization of glucose and xylose from lignocellulosic biomasses. Study of the glucose sensing pathway helps to construct glucose repression-released yeast strains and enhance the utilization of lignocellulosic biomasses.ResultsHerein, the glucose sensor/receptor repressor (SRR) pathway of Kluyveromyces marxianus which mainly consisted of KmSnf3, KmGrr1, KmMth1, and KmRgt1 was studied. The disruption of KmSNF3 led to a release of glucose repression, enhanced xylose consumption and did not result in deficient glucose utilization. Over-expression of glucose transporter gene restored the mild decrease of glucose utilization ability of Kmsnf3 strain to a similar level of the wildtype strain but did not restore glucose repression. Therefore, the repression on glucose transporter is parallel to glucose repression to xylose and other alternative carbon utilization. KmGRR1 disruption also released glucose repression and kept glucose utilization ability, although its xylose utilization ability was very weak with xylose as sole carbon source. The stable mutant of KmMth1-ΔT enabled the release of glucose repression irrespective that the genetic background was Kmsnf3, Kmmth1, or wildtype. Disruption of KmSNF1 in the Kmsnf3 strain or KmMTH1-ΔT overexpression in Kmsnf1 strain kept constitutive glucose repression, indicating that KmSNF1 was necessary to release the glucose repression in both SRR and Mig1-Hxk2 pathway. Finally, overexpression of KmMTH1-ΔT released the glucose repression to xylose utilization in S. cerevisiae.ConclusionThe glucose repression-released K. marxianus strains constructed via a modified glucose SRR pathway did not lead to a deficiency in the utilization ability of sugar. The obtained thermotolerant, glucose repression-released, and xylose utilization-enhanced strains are good platforms for the construction of efficient lignocellulosic biomass utilization yeast strains.

Biosynthesis and properties of polyhydroxyalkanoates synthesized from mixed C5 and C6 sugars obtained from hardwood hydrolysis

Glucose and xylose are fermentable sugars readily available from lignocellulosic biomass, and are a sustainable carbon substrate supporting industrial biotechnology. Three strains were assessed in this work – Paraburkholderia sacchari, Hydrogenophaga pseudoflava, and Bacillus megaterium – for their ability to uptake both C5 and C6 sugars contained in a hardwood hydrolysate produced via a thermomechanical pulping-based process with concomitant production of poly(3-hydroxyalkanoate) (PHA) biopolymers. In batch conditions, B. megaterium showed poor growth after 12 h, minimal uptake of xylose throughout the cultivation, and accumulated a maximum of only 25 % of the dry biomass as PHA. The other strains simultaneously utilized both sugars, although glucose uptake was faster than xylose. From hardwood hydrolysate, P. sacchari accumulated 57 % of its biomass as PHA within 24 h, whereas H. pseudoflava achieved an intracellular PHA content of 84 % by 72 h. The molecular weight of the PHA synthesized by H. pseudoflava (520.2 kDa) was higher than that of P. sacchari (265.5 kDa). When the medium was supplemented with propionic acid, the latter was rapidly consumed by both strains and incorporated as 3-hydroxyvalerate subunits into the polymer, demonstrating the potential for production of polymers with improved properties and value. H. pseudoflava incorporated 3-hydroxyvalerate subunits with at least a 3-fold higher yield, and produced polymers with higher 3-hydroxyvalerate content than P. sacchari. Overall, this work has shown that H. pseudoflava can be an excellent candidate for bioconversion of lignocellulosic sugars to PHA polymers or copolymers as part of an integrated biorefinery.

Potential xylose transporters regulated by CreA improved lipid yield and furfural tolerance in oleaginous yeast Saitozyma podzolica zwy-2-3

Lignocellulose's hydrolysate, a significant renewable source, contains xylose and furfural, making it challenging for industrial production of oleaginous yeast. On xylose fermentation with furfural treatment, OE::DN7263 and OE::DN7661 increased lipid yield and furfural tolerance versus WT, while, which of OE::CreA were decreased owing to CreA regulating DN7263 and DN7661 negatively. OE::CreA generated reactive oxygen species (ROS) causing oxidative damage. OE::DN7263, OE::DN7661, and ΔCreA reduced furfural via NADH; while ΔCreA produced less ROS and OE::DN7263, and OE::DN7661 scavenged ROS quickly, minimizing oxidative damage. Overall, CreA knockout increased DN7263 and DN7661 expression to facilitate xylose assimilation, enhancing NADH generation and ROS clearance. Finally, with mixed sugar fermentation, ΔCreA and OE::DN7263′s biomass and lipid yield rose without furfural addition, while that of ΔCreA remained higher than WT after furfural treatment. These findings revealed how oleaginous yeast zwy-2–3 resisted furfural stress and indicated ΔCreA and OE::DN7263 might develop into robust industrial chassis strains.

Developing high-dimensional machine learning models to improve generalization ability and overcome data insufficiency for mixed sugar fermentation simulation

Biorefinery can be promoted by building accurate machine learning models. This work proposed a strategy to enhance model’s generalization ability and overcome insufficient data conditions for mixed sugar fermentation simulation. Multiple inputs single output models, using initial glucose, initial xylose, and time together as inputs, have higher generalization ability than single input single output models with time as sole input in predicting glucose, xylose, ethanol, or biomass separately. Multiple inputs multiple outputs models, integrating outputs, enhanced model accuracy and resulted in an average R2 at 0.99. To overcome data insufficiency conditions, consensus yeast (CY) model, through consolidating data from 4 yeasts, obtained R2 at 0.90. By adjusting the pretrained CY model, the model can save more than 50% data and get R2 at 0.95 and 0.93 for yeast and bacterial fermentation simulation. The strategy can expand the application range and save costs of data curation for ANN models.

Comparison of alternative neutral detergent fiber methods to the AOAC definitive method

Neutral detergent fiber (NDF) is the most commonly reported metric for fiber in dairy cattle nutrition. An empirical method, NDF is defined by the procedure used to measure it. The current definitive method for NDF treated with amylase (aNDF) is AOAC Official Method 2002.04 performed on dried samples ground through the 1-mm screen of a cutting mill with refluxing and then filtration through Gooch crucibles without (AOAC-; reference method) or with (AOAC+) a glass fiber filter filtration aid. Other methods in use include grinding materials through the 1-mm screen of an abrasion mill, using filtration through a Buchner funnel with a glass fiber filter (Buch), and use of the ANKOM system (ANKOM Technology, Macedon, NY) that simultaneously extracts and filters samples through filter bags with larger (F57) or smaller (F58) particle size retentions. Our objective was to compare the AOAC and alternative methods using samples ground through the 1-mm screens of cutting or abrasion mills. Materials analyzed were 2 alfalfa silages, 2 corn silages, dry ground and high-moisture corn grains, mixed grass hay, ryegrass silage, soybean hulls, calf starter, and sugar beet pulp. Samples were run in duplicate in replicate analytical runs performed on different days by experienced technicians. Compared with cutting mill-ground samples, the aNDF% of dry matter results from abrasion mill-ground samples were or tended to be lower for 8 of 11 samples. Method affected aNDF% results for all materials, with method × grind interactions for 6 of 11 samples. For ash-free aNDF% assessed with cutting mill-ground materials, a priori selected contrasts showed that the number of materials for which methods differed or tended to differ from the AOAC methods were 4 (Buch), 8 (F57), and 3 (F58); and 3 for AOAC- versus AOAC+. However, statistically different does not necessarily mean substantially different. For a given feed and grind, a positive value for the absolute difference between the AOAC- mean and an alternative method mean minus 2 times the standard deviation of AOAC- suggests that values for the alternative method fall outside of the range of results likely to be observed for the reference method. The number of observed positive values for materials processed with cutting and abrasion mills, respectively, were 0 and 2 (AOAC+); 2 and 2 (Buch); 8 and 10 (F57); 4 and 7 (F58); and 0 and 4 (AOAC-). With the materials tested, methods in order of agreement with the reference method were Buch, F58, and F57, which often gave lower values. The AOAC+ gave results similar to AOAC-, substantiating it as an allowed modification of AOAC-. Best agreement between the reference method and variant NDF methods was achieved with the 1-mm screen cutting mill grind. The 1-mm abrasion mill grind produced more aNDF% results that were lower than the reference method but with fewer differences when filter particle retention size was smaller. The use of filters that retain finer particles could be explored to improve comparability of variant NDF methods and grinds. Further evaluation with an expanded set of materials is warranted.

Sequential fermentation with in situ distillation for bioethanol and xylitol production from mixed sugars: a novel approach for lignocellulosic material-based biorefineries

Sequential fermentation with in situ distillation for bioethanol and xylitol production from mixed sugars: a novel approach for lignocellulosic material-based biorefineries

A comprehensive screening platform of wood-derived sugars for sophorolipid production: Predictive modelling, sterilization methods and analysis of feedstock composition

Sophorolipid production using conventional food-grade feedstocks such as glucose and rapeseed oil can have detrimental impacts on food supply and commodity prices. The increasing complexity of alternative feeds necessitates efficient management of nutritional (substrate and inhibitor content) and physical (viscosity, particulates) characteristics. To address this, a screening platform was applied that uses predictive modelling to customize the fermentation media composition based on feed substrate content, while employing different preparation methods such as tangential flow filtration or autoclaving to mitigate particulate loading and prevent the formation of inhibitory by-products. To validate the platform, three lignocellulosic sugars (Fibenol OÜ) were tested, including the glucose-rich (C6), xylose-rich (C5), and mixed (C5/C6) sugars. Under the tailored media conditions, the C6 wood-sugar produced 47.12 g/L and 44.33 g/L average sophorolipid with tangential flow filtration and autoclave sterilization, respectively. The C5/C6 wood-sugar only produced sophorolipid with tangential flow filtration (40.15 g/L) whilst the C5 wood-sugar did not produce sophorolipids with either sterilization method. Comparatively, autoclaved glucose produced 33.06 g/L average sophorolipid under conditions matching the C6 and C5 wood-sugars. The combination of predictive profiling and preparation method comparisons allows for effective screening of potentially productive fermentation feeds, with the application of tangential flow filtration for feeds being reported for the first time.

Excessive Nectar Intake from <i>Lantana camara</i> L. Punish Honeybee, <i>Apis mellifera</i> during the Dearth Period

A study was conducted to scientifically validate the beekeeper’s perceptions about toxicity of Lantana camara to honey bee, Apis mellifera. Firstly, the floral visits to the source plant during honey flow and dearth period were recorded and correlated with the observed mortality in the bee colonies. A strong correlation was observed between floral visits and bee mortality. Lantadene was extracted and its effect was demonstrated through a randomized experiment to investigate the effect of lantadene on bee colonies. For this, colonies were fed with different concentrations of lantadene mixed sugar candy and the mortality was compared with those fed without it. It was found that excessive floral visits and nectar intake during dearth period is associated with bee mortality through lantadene.

Fermentation development using fruit waste derived mixed sugars for poly(3-hydroxybutyrate) production and property evaluation

Free sugars from fruit wastes were evaluated for the production of poly(3-hydroxybutyrate) (PHB) in Paraburkholderia sacchari fed-batch bioreactor fermentations. Different initial sugar concentration, carbon to inorganic phosphorus (C/IP) ratio, IP addition during feeding and volumetric oxygen transfer coefficient (kLa) were evaluated to promote PHB production. The highest intracellular PHB accumulation (66.6%), PHB concentration (108.3 g/L), productivity (3.28 g/(L·h)) and yield (0.33 g/g) were achieved at 40 g/L initial sugars, C/IP 26.5, 202.6 h−1kLa value and 20% IP supplementation in the feeding solution. The effect of different microbial mass harvesting time on PHB properties showed no influence in weight average molecular weight and thermal properties. The harvest time influenced the tensile strength that was reduced from 28.7 MPa at 22 h to 13.3 MPa at 36 h. The elongation at break and Young’s modulus were in the range 3.6–14.8% and 830–2000 MPa, respectively.

Lipid Accumulation by Snf-β Engineered Mucor circinelloides Strains on Glucose and Xylose.

Sucrose non-fermenting 1 (SNF1) protein kinase plays the regulatory roles in the utilization of selective carbon sources and lipid metabolism. Previously, the role of β subunit of SNF1 in lipid accumulation was evaluated by overexpression and knockout of Snf-β in oleaginous fungus M. circinelloides. In the present study, the growth and lipid accumulation of Snf-β overexpression and knockout strains were further analyzed and compared with glucose or xylose as a single or mixed carbon sources. The results showed that the lipid contents in Snf-β knockout strain improved by 23.2% (for glucose), 28.4% (for xylose), and 30.5% (for mixed glucose and xylose) compared with that of the control strain, respectively. The deletion of Snf-β subunit also altered the transcriptional level of acetyl-CoA carboxylase (ACC). The highest transcriptional levels of ACC1 in Snf-β knockout strain at 24h were increased by 2.4-fold (for glucose), 2.8-fold (for xylose), and 3.1-fold (for mixed glucose and xylose) compared with that of the control strain, respectively. Our results indicated that Snf-β subunit enhanced lipid accumulation through the regulation of ACC1 in response to xylose or mixed sugars of glucose and xylose more significantly than that of response to glucose. This is the first study to explore the effect of Snf-β subunit of M. circinelloides in regulating lipid accumulation responding to different carbon nutrient signals of glucose and xylose. This study provides a foundation for the future application of the Snf-β engineered strains in lipid production from lignocellulose.

75 Effect of probiotic supplementation on intestinal permeability in subjects with overweight and obesity: A systematic review of randomized controlled trials

OBJECTIVES/GOALS: Obesity is associated with gut dysbiosis, inflammation, and increased intestinal permeability. Probiotic consumption may reverse these outcomes. The goal of this study is to evaluate the evidence linking probiotic consumption to changes in intestinal permeability in subjects with overweight or obesity. METHODS/STUDY POPULATION: Articles were searched in Pubmed, Web of Science, and CAB Direct through February 2022 using search terms: intestinal permeability, overweight or obesity, and probiotic supplementation. 694 articles were exported, and 289 duplicates were identified. Titles and abstract were screened in the 405 remaining references by two investigators to determine eligibility. Eligible studies had data extracted on study participant characteristics, probiotic strain used, probiotic dosage, length of intervention, and intestinal barrier outcomes. Results were summarized in tabular form based on intestinal permeability response to probiotics. Quality of the studies was assessed based on Cochrane–Risk of Bias’ tool (RoB2). RESULTS/ANTICIPATED RESULTS: Thirteen eligible studies were identified. Probiotic genera included Akkermansia, Bifidobacterium, Lactobacillus, Streptococcus, Lactococcus, and Bacillus. Single strain probiotics were used in 3 studies, while the other 10 used multi-strain formulas. Dosage and length of probiotic supplementation ranged from 2.4 x 10^7 to 5 x 10^10 CFU/person/day and 3 to 26 weeks, respectively. The most widely used gut permeability outcomes were serum lipopolysaccharide (LPS) (n=10) and mixed sugar solution consumption with urine analysis (n=6). Five of the 10 studies reported decreases in serum LPS following probiotic consumption, while the other 5 showed no effect. Urinary lactulose/mannitol ratio decreased in 1 of the 4 studies, and urinary lactulose percent decreased in 2 studies. DISCUSSION/SIGNIFICANCE: Probiotic supplementation may be remediating an obesity-induced increase in intestinal permeability as evidenced from the effect on serum LPS and mixed sugar solution assays. However, additional studies are needed to further clarify which strain of probiotic bacteria is most effective and the optimal intervention length in subjects with obesity.

Two Anecdotes of Pie

Two Anecdotes of Pie Donald Platt I Wallace Stevens lovedpie. His neighbor brought him a chocolatesilk pie, dark as a starless night. “What do youcall this pie?” he asked, he who had “placed a jarin Tennessee.” She smiled and replied,“Heavenly Pie.” That jar had tamed “the slovenlywilderness” around him. “Well,” he said,raising a piece on his fork slowly towardshis mouth, hungry after having walked home froma long day writing surety bonds at theHartford Accident and IndemnityCompany on Asylum Avenue,“Open the pearly gates.” II I am so loved byyou, who walk through rain [End Page 106] for twenty minutesto my apartment, carrying ina glass pie pan wrapped in a soft burlapbag to keep it warm from the oven, onewhole, paw-paw, lemon grass, and ginger pie.You grew the paw-paws, shook them when ripe downfrom the tree. Deseeded them. Scooped out theirbutter-colored flesh. Puréed it. Mixed itwith vanilla sugar, spices, whole milk, eggs.Poured it into its graham-cracker crust.Baked it until it turned golden as theharvest moon rising over a lake, castingits moonlight on the dark water to makean upside-down exclamation pointof light the color of gnarled ginger root.You are allergic [End Page 107] to paw-paws. You stayhungry and smile while you watch me devour onelarge slice, then clamor for more caramelizedmoonlight. [End Page 108] Donald Platt Lafayette, Indiana Copyright © 2023 Johns Hopkins University Press

Production of acetoin and its derivative tetramethylpyrazine from okara hydrolysate with Bacillus subtilis

Okara, a renewable biomass resource, is a promising fermentative raw material for the bio-production of value-added chemicals due to its abundance and low-costs. we developed a process for the enzymatic hydrolysis of okara, and then engineered Bacillus subtilis to utilize mixed sugars to produce acetoin in okara hydrolysis without the addition of a supplemental nitrogen source. Okara was initially hydrolyzed with cellulase, β-glucosidase, and pectinase to obtain okara hydrolysate containing mixed sugars (32.78 ± 0.23 g/L glucose, 1.43 ± 0.064 g/L arabinose, 7.74 ± 0.11 g/L galactose) and amino acids. In this study, Bacillus subtilis 168 was used as the acetoin-producing strain, and the key genes bdhA and acoA of the acetoin catabolism pathway were knocked out to improve the fermentation yield of acetoin. In order to utilize the galactose in the hydrolysate, the recombinant strain BS03 (Bacillus subtilis168∆bdhA∆acoA) was used to overexpress the arabinose transporter-encoding gene (araE) drive heterologous expression of the Leloir pathway gene (galKTE). The corn dry powder concentration was optimized to 29 g/L in the reducing sugar okara hydrolysate. The results show that the recombinant bacterium BS03 could still synthesize 11.79 g/L acetoin without using corn dry powder as a nitrogen source. Finally, using okara enzymatic hydrolysate as the carbon and nitrogen source, 11.11 g/L and 29.7 g/L acetoin were obtained by batch fermentation and fed-batch fermentation, respectively, which was further converted to 5.33 g/L and 13.37 g/L tetramethylpyrazine (TTMP) by reaction with an ammonium salt.

Bifunctional Solid Lewis Acid–Base Catalysts for Efficient Conversion of the Glucose–Xylose Mixture to Methyl Lactate

Sugars produced from lignocellulose hydrolyzate are usually a mixture, of which glucose and xylose are the most abundant. Herein, a bifunctional solid catalyst (Mg-Sn-Beta zeolite) with Lewis (L) acidity and L basicity is developed, which can efficiently catalyze the glucose–xylose mixture to methyl lactate (MLA). This avoids the economic cost and cumbersome operation caused by separating mixed sugars. The retro-aldol condensation and aldol condensation are two major steps in converting glucose and/or xylose to MLA. L acid sites and L base sites in Mg-Sn-Beta zeolite are favorable for the above two steps. 1Mg-Sn-Beta-x and yMg-Sn-Beta-100 with different contents of L acid sites and L base sites were characterized via various techniques. In the conversion of glucose–xylose mixture to MLA, a considerable yield (52%) was obtained over 2Mg-Sn-Beta-100 compared with that on Sn-Beta-100 (25%). Besides, 2Mg-Sn-Beta-100 exhibited excellent stability and reusability during five reaction runs.

Identification of traits to improve co-assimilation of glucose and xylose by adaptive evolution of Spathaspora passalidarum and Scheffersomyces stipitis yeasts.

Lignocellulosic biomass is a renewable raw material for producing several high-value-added chemicals and fuels. In general, xylose and glucose are the major sugars in biomass hydrolysates, and their efficient utilization by microorganisms is critical for an economical production process. Yeasts capable of co-consuming mixed sugars might lead to higher yields and productivities in industrial fermentation processes. Herein, we performed adaptive evolution assays with two xylose-fermenting yeasts, Spathaspora passalidarum and Scheffersomyces stipitis, to obtain derived clones with improved capabilities of glucose and xylose co-consumption. Adapted strains were obtained after successive growth selection using xylose and the non-metabolized glucose analog 2-deoxy-D-glucose as a selective pressure. The co-fermentation capacity of evolved and parental strains was evaluated on xylose-glucose mixtures. Our results revealed an improved co-assimilation capability by the evolved strains; however, xylose and glucose consumption were observed at slower rates than the parental yeasts. Genome resequencing of the evolved strains revealed genes affected by non-synonymous variants that might be involved with the co-consumption phenotype, including the HXT2.4 gene that encodes a putative glucose transporter in Sp. passalidarum. Expression of this mutant HXT2.4 in Saccharomyces cerevisiae improved the cells' co-assimilation of glucose and xylose. Therefore, our results demonstrated the successful improvement of co-fermentation through evolutionary engineering and the identification of potential targets for further genetic engineering of different yeast strains. KEY POINTS: • Laboratory evolution assay was used to obtain improved sugar co-consumption of non-Saccharomyces strains. • Evolved Sp. passalidarum and Sc. stipitis were able to more efficiently co-ferment glucose and xylose. • A mutant Hxt2.4 permease, which co-transports xylose and glucose, was identified.

Effect of Carbon Sources on Glutamate Production from Corynebacterium glutamicum 2262

A comparative study between natural and synthetic environments is carried out by realizing six fermentation experiments in batch culture. The objective of this study is to consider the effect of carbon sources on growth and the production of glutamic acid by Corynebacterium glutamicum 2262. The difference between the culture media lies in the carbon source. Two natural environments of date juice, one of which is treated with invertase to hydrolyse sucrose with a concentration of total sugars of 88 g/L. Four synthetic media with a concentration of 34 g/L sugars: medium containing mixed sugars (glucose + fructose + sucrose) with rates proportional to that of date juice, the other three media are composed of a single sugar (either glucose, fructose, or sucrose). The results showed that Corynebacterium glutamicum is able to use the three sugars whether they are single or mixed, although the best results of glutamate production (8.41 g/L) are obtained on the mixture of three sugars, which explains the interest and valorisation of date waste. On the other hand, the date juice-based media are shown to have a glutamate concentration of 7.98 g/L during the hydrolysis of sucrose of date juice.