Surface-enhanced Raman spectroscopy for the characterization of xylanases enzyme.

Xylanases are essential hydrolytic enzymes which break down the plant cell wall polysaccharide, xylan composed of D-xylose monomers. Surface-enhanced Raman Spectroscopy (SERS) was utilized for the characterization of interaction of xylanases with xylan at varying concentrations. The study focuses on the application of SERS for the characterization of enzymatic activity of xylanases causing hydrolysis of Xylan substrate with increase in its concentration which is substrate for this enzyme in the range of 0.2% to 1.0%. SERS differentiating features are identified which can be associated with xylanases treated with different concentrations of xylan. SERS measurements were performed using silver nanoparticles as SERS substrate to amplify Raman signal intensity for the characterization of xylan treated with xylanases. Principal Component Analysis (PCA) and Partial Least Square Discriminant Analysis (PLS-DA) were applied to analyze the spectral data to analyze differentiation between the SERS spectra of different samples. Mean SERS spectra revealed significant differences in spectral features particularly related to carbohydrate skeletal mode and O-C-O and C-C-C ring deformations. PCA scatter plot effectively differentiates data sets, demonstrating SERS ability to distinguish treated xylanases samples and the PC-loadings plot highlights the variables responsible for differentiation. PLS-DA was employed as a quantitative classification model for treated xylanase enzymes with increasing concentrations of xylan. The values of sensitivity, specificity, and accuracy were found to be 0.98%, 0.99%, and 100% respectively. Moreover, the AUC value was found to be 0.9947 which signifies the excellent performance of PLS-DA model. SERS combined with multivariate techniques, effectively characterized and differentiated xylanase samples as a result of interaction with different concentrations of the Xylan substrate. The identified SERS features can help to characterize xylanases treated with various concentrations of xylan with promising applications in the bio-processing and biotechnology industries.

Multilevel systemic engineering of Bacillus licheniformis for efficient production of acetoin from lignocellulosic hydrolysates.

Bio-refining lignocellulosic resource offers a renewable and sustainable approach for producing biofuels and biochemicals. However, the conversion efficiency of lignocellulosic resource is still challenging due to the intrinsic inefficiency in co-utilization of xylose and glucose. In this study, the industrial bacterium Bacillus licheniformis was engineered for biorefining lignocellulosic resource to produce acetoin. First, adaptive evolution was conducted to improve acetoin tolerance, leading to a 19.6 % increase in acetoin production. Then, ARTP mutagenesis and 60Co-γ irradiation was carried out to enhance the production of acetoin, obtaining 73.0 g/L acetoin from glucose. Further, xylose uptake and xylose utilization pathway were rewired to facilitate the co-utilization of xylose and glucose, enabling the production of 60.6 g/L acetoin from glucose and xylose mixtures. Finally, this efficient cell factory was utilized for acetoin production from lignocellulosic hydrolysates with the highest titer of 68.3 g/L in fed-batch fermentation. This strategy described here holds great applied potential in the biorefinery of lignocellulose for the efficient synthesis of high-value chemicals.

Bacteroides ovatus alleviates dysbiotic microbiota-induced graft-versus-host disease.

Acute lower gastrointestinal GVHD (aLGI-GVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation. Although the intestinal microbiota is associated with the incidence of aLGI-GVHD, how the intestinal microbiota impacts treatment responses in aLGI-GVHD has not been thoroughly studied. In a cohort of patients with aLGI-GVHD (n = 37), we found that non-response to standard therapy with corticosteroids was associated with prior treatment with carbapenem antibiotics and a disrupted fecal microbiome characterized by reduced abundances of Bacteroides ovatus. In a murine GVHD model aggravated by carbapenem antibiotics, introducing B. ovatus reduced GVHD severity and improved survival. These beneficial effects of Bacteroides ovatus were linked to its ability to metabolize dietary polysaccharides into monosaccharides, which suppressed the mucus-degrading capabilities of colonic mucus degraders such as Bacteroides thetaiotaomicron and Akkermansia muciniphila, thus reducing GVHD-related mortality. Collectively, these findings reveal the importance of microbiota in aLGI-GVHD and therapeutic potential of B. ovatus.

[Construction of microbial cell factories for synthesizing value-added chemicals with xylose].

Lignocellulose is the most abundant renewable resource on earth. Constructing microbial cell factories for synthesizing value-added chemicals with lignocellulose is the key to realize green biomanufacturing. Xylose is the second most fermentable sugar in lignocellulose after glucose. Building microbial cell factories that can efficiently metabolize xylose is of great significance to achieve full utilization of lignocellulose. However, the lower metabolism efficiency of xylose than that of glucose in most microorganisms limits the application of xylose. In recent years, the deepening understanding of microbial metabolic mechanisms and the continuous advancement of synthetic biology have greatly improved the efficiency of microbial metabolism of xylose and expanded the spectrum of xylose-derived products. This article introduces several xylose metabolic pathways that exist in the nature and the derived products, summarizes the strategies for constructing recombinant strains that can co-utilize xylose and glucose, and reviews the research progress in the application of lignocellulose hydrolysates in the synthesis of target products. Finally, this article discusses the current technical bottlenecks and prospects the future development directions in this field.

[Metabolic engineering for the efficient co-utilization of glucose and xylose].

Microbial production of chemicals from renewable biomass has emerged as a crucial route for sustainable bio-manufacturing. Lignocellulose with a renewable property and wide sources is supposed to be a promising feedstock for the second-generation biorefinery. The efficient co-utilization of mixed sugars from lignocellulosic hydrolysates represents one of the key challenges in reducing the production cost. However, most microorganisms prefer glucose over xylose due to carbon catabolite repression, which constrains the efficiency of lignocellulosic conversion. Therefore, developing the microbial platforms capable of simultaneously utilizing glucose and xylose is paramount for economically viable industrial-scale production. This article reviews the key strategies and studies of metabolic engineering for promoting efficient co-utilization of glucose and xylose by microorganisms. The representative strategies include relieving glucose repression, enhancing xylose transport, constructing xylose metabolic pathways, and directed evolution.

Xylose Incorporated in Unsymmetrical Gold(I) N-Heterocyclic Carbene Complexes: Synthesis, Characterization and Antibacterial Activity.

A series of Au(I) complexes containing unsymmetrical N-heterocyclic carbene (imidazolylidene and benzimidazolylidene) functionalized with a xyloside group and an alkyl moiety (methyl and mesityl) was prepared using efficient procedures from D-xylose. Their characterization was carried out in solution by multinuclear NMR, HR-MS spectrometry and cyclic voltammetry, as well as in the solid state by means of single crystal X-ray diffraction analysis for two of them. Evaluation of their ability to inhibit bacterial growth showed a preference for a Gram-positive strain, Staphylococcus aureus, over a Gram-negative strain, Pseudomonas aeruginosa.

Integrated production of xylose and docosahexaenoic acid from hemicellulose and cellulose in corncob.

Exploring efficient and comprehensive utilization of agricultural waste to produce high value-added products has been global research hotspot. In this study, a novel process for integrated production of xylose and docosahexaenoic acid (DHA) from hemicellulose and cellulose in corncob was developed. Corncob was treated with dilute H2SO4 at 121 °C for 1 h and xylose was readily produced with a recovery yield of 79.35 %. The corncob residue was then subject to alkali pretreatment under optimized conditions of 0.1 g NaOH/g dry solid, 60 °C for 2 h, and the contents of cellulose, hemicellulose, and lignin in the resulting residue were 87.49 %, 7.58 % and 2.31 %, respectively. The cellulose in the residue was easily hydrolyzed by cellulase, yielding 74.87 g/L glucose with hydrolysis efficiency of 77.02 %. Remarkably, the corncob residue hydrolysate supported cell growth and DHA production in Schizochytrium sp. ATCC 20888 well, and the maximum biomass of 32.71 g/L and DHA yield of 4.63 g/L were obtained, with DHA percentage in total fatty acids of 36.89 %. This study demonstrates that the corncob residue generated during xylose production, rich in cellulose, can be effectively utilized for DHA production by Schizochytrium sp., offering a cost-effective and sustainable alternative to pure glucose.

Molecular Modification Enhances Xylose Uptake by the Sugar Transporter KM_SUT5 of Kluyveromyces marxianus.

This research cloned and expressed the sugar transporter gene KM_SUT5 from Kluyveromyces marxianus GX-UN120, which displayed remarkable sugar transportation capabilities, including pentose sugars. To investigate the impact of point mutations on xylose transport capacity, we selected four sites, predicted the suitable amino acid sites by molecular docking, and altered their codons to construct the corresponding mutants, Q74D, Y195K, S460H, and Q464F, respectively. Furthermore, we conducted site-directed truncation on six sites of KM_SUT5p. The molecular modification resulted in significant changes in mutant growth and the D-xylose transport rate. Specifically, the S460H mutant exhibited a higher growth rate and demonstrated excellent performance across 20 g L-1 xylose, achieving the highest xylose accumulation under xylose conditions (49.94 µmol h-1 gDCW-1, DCW mean dry cell weight). Notably, mutant delA554-, in which the transporter protein SUT5 is truncated at position delA554-, significantly increased growth rates in both D-xylose and D-glucose substrates. These findings offer valuable insights into potential modifications of other sugar transporters and contribute to a deeper understanding of the C-terminal function of sugar transporters.

Metabolic bottlenecks of Pseudomonas taiwanensis VLB120 during growth on d-xylose via the Weimberg pathway.

The microbial production of value-added chemicals from renewable feedstocks is an important step towards a sustainable, bio-based economy. Therefore, microbes need to efficiently utilize lignocellulosic biomass and its dominant constituents, such as d-xylose. Pseudomonas taiwanensis VLB120 assimilates d-xylose via the five-step Weimberg pathway. However, the knowledge about the metabolic constraints of the Weimberg pathway, i.e., its regulation, dynamics, and metabolite fluxes, is limited, which hampers the optimization and implementation of this pathway for bioprocesses. We characterized the Weimberg pathway activity of P. taiwanensis VLB120 in terms of biomass growth and the dynamics of pathway intermediates. In batch cultivations, we found excessive accumulation of the intermediates d-xylonolactone and d-xylonate, indicating bottlenecks in d-xylonolactone hydrolysis and d-xylonate uptake. Moreover, the intermediate accumulation was highly dependent on the concentration of d-xylose and the extracellular pH. To encounter the apparent bottlenecks, we identified and overexpressed two genes coding for putative endogenous xylonolactonases PVLB_05820 and PVLB_12345. Compared to the control strain, the overexpression of PVLB_12345 resulted in an increased growth rate and biomass generation of up to 30 % and 100 %, respectively. Next, d-xylonate accumulation was decreased by overexpressing two newly identified d-xylonate transporter genes, PVLB_18545 and gntP (PVLB_13665). Finally, we combined xylonolactonase overexpression with enhanced uptake of d-xylonate by knocking out the gntP repressor gene gntR (PVLB_13655) and increased the growth rate and biomass yield by 50 % and 24 % in stirred-tank bioreactors, respectively. Our study contributes to the fundamental knowledge of the Weimberg pathway in pseudomonads and demonstrates how to encounter the metabolic bottlenecks of the Weimberg pathway to advance strain developments and cell factory design for bioprocesses on renewable feedstocks.

One-pot conversion of xylose to 1,2-pentanediol catalyzed by an organic acid-assisted Pt/NC in aqueous phase.

The direct synthesis of 1,2-pentanediol (1,2-PeD) from renewable xylose and its derivatives derived from hemicellulose is appealing yet challenging due to its low selectivity for the target product. In this study, one-pot catalytic conversion of xylose to 1,2-PeD was performed by using nitrogen-doped carbon (NC) supported Pt catalysts with the assistance of organic acids. A remarkable yield of 49.3% for 1,2-PeD was achieved by reacting 0.1869 g xylose in 30 mL water at 200 °C under a hydrogen pressure of 3 MPa for 8 h in the presence of 0.1 g of 2.5Pt/NC600 catalyst and 0.1869 g propanoic acid co-catalyst. The presence of vicinal Pt-acid pair sites on the surface of the 2.5Pt/NC600 catalyst exhibited a synergistic effect in promoting the hydrogenation of furfural to furfuryl alcohol intermediate and subsequent hydrogenation and ring-opening reactions leading to the formation of 1,2-PeD. The addition of organic acids, may serve as both acid catalyst for dehydration of xylose and hydrogen donor for hydrogenation of furfural and furfuryl alcohol, thereby promoting the one-pot conversion of xylose to 1,2-PeD. Remarkably, the 2.5Pt/NC600 catalyst demonstrated outstanding catalytic performance and good reusability over five consecutive cycles without significant deactivation.

Experimental evolution reveals an effective avenue for d-lactic acid production from glucose-xylose mixtures via enhanced Glk activity and a cAMP-independent CRP mutation.

d-Lactic acid holds significant industrial importance due to its versatility and serves as a crucial component in the synthesis of environmentally friendly and biodegradable thermal-resistant poly-lactic acid. This polymer exhibits promising potential as a substitute for nonbiodegradable, petroleum-based plastics. The production of d-lactic acid from lignocellulosic biomass, a type of biorenewable and nonfood resources, can lower costs and improve product competitiveness. Glucose and xylose are the most abundant sugar monomers in lignocellulosic biomass materials. Despite Escherichia coli possessing native xylose catabolic pathways and transport, their ability to effectively utilize xylose is often hindered in the presence of glucose. Here, the E. coli strain Rec1.0, previously engineered to overcome carbon catabolite repression, was selected as the initial strain for reengineering to produce d-lactic acid. An adaptive evolution approach was employed to achieve highly efficient fermentation of glucose-xylose mixtures. The resulting strain, QJL010, could produce d-lactic acid of 87.5 g/L with a carbon yield of 0.99 mol/mol. Notably, the consumption rates of glucose and xylose reached 0.75 and 0.82 g/gDCW/h, respectively. Further analysis revealed that increased Glk activity, resulting from glk mutations (A142V and R188H), along with their upregulated expression, contributed to an elevated glucose consumption rate. Additionally, a CRP G141D mutation, cAMP-independent, stimulated the expression of the xylR, xylE, and galABC* genes, resulting in an accelerated xylose consumption rate. These findings provide valuable support for the utilization of E. coli platform strains in the production of value-added chemicals from lignocellulosic biomass.

Efficient sugar utilization and high tolerance to inhibitors enable Rhodotorula toruloides C23 to robustly produce lipid and carotenoid from lignocellulosic feedstock.

The utilization of lignocellulosic substrates for microbial oil production by oleaginous yeasts has been evidenced as an economically viable process for industrial-scale biodiesel preparation. Efficient sugar utilization and tolerance to inhibitors are critical for lipid production from lignocellulosic substrates. This study investigated the lignocellulosic sugar utilization and inhibitor tolerance characteristics of Rhodotorula toruloides C23. The results demonstrated that C23 exhibited robust glucose and xylose assimilation irrespective of their ratios, yielding over 21 g/L of lipids and 11 mg/L of carotenoids. Furthermore, C23 exhibited high resistance and efficiently degradation towards toxic inhibitors commonly found in lignocellulosic hydrolysates. The potential molecular mechanism underlying xylose metabolism in C23 was explored, with several key enzymes and signal regulation pathways identified as potentially contributing to its superior lipid synthesis performance. The study highlights R. toruloides C23 as a promising candidate for robust biofuel and carotenoid production through direct utilization of non-detoxified lignocellulosic hydrolysates.

Host cell wall composition and localized microenvironment implicated in resistance to basal stem degradation by lettuce drop (Sclerotinia minor).

BACKGROUND: Sclerotinia spp. are generalist fungal pathogens, infecting over 700 plant hosts worldwide, including major crops. While host resistance is the most sustainable and cost-effective method for disease management, complete resistance to Sclerotinia diseases is rare. We recently identified soft basal stem as a potential susceptibility factor to Sclerotinia minor infection in lettuce (Lactuca sativa) under greenhouse conditions. RESULTS: Analysis of stem and root cell wall composition in five L. sativa and one L. serriola accessions with varying growth habits and S. minor resistance levels revealed strong association between hemicellulose constituents, lignin polymers, disease phenotypes, and basal stem mechanical strength. Accessions resistant to basal stem degradation consistently exhibited higher levels of syringyl, guaiacyl, and xylose, but lower levels of fucose in stems. These findings suggest that stem cell wall polymers recalcitrant to breakdown by lignocellulolytic enzymes may contribute to stem strength-mediated resistance against S. minor. CONCLUSIONS: The lignin content, particularly guaiacyl and syringyl, along with xylose could potentially serve as biomarkers for identifying more resistant lettuce accessions and breeding lines. Basal stem degradation by S. minor was influenced by localized microenvironment conditions around the stem base of the plants.

Riboflavin overproduction on lignocellulose hydrolysate by the engineered yeast Candida famata.

Lignocellulose (dry plant biomass) is an abundant cheap inedible residue of agriculture and wood industry with great potential as a feedstock for biotechnological processes. Lignocellulosic substrates can serve as valuable resources in fermentation processes, allowing the production of a wide array of chemicals, fuels, and food additives. The main obstacle for cost-effective conversion of lignocellulosic hydrolysates to target products is poor metabolism of the major pentoses, xylose and L-arabinose, which are the second and third most abundant sugars of lignocellulose after glucose. We study the oversynthesis of riboflavin in the flavinogenic yeast Candida famata and found that all major lignocellulosic sugars, including xylose and L-arabinose, support robust growth and riboflavin synthesis in the available strains of C. famata. To further increase riboflavin production from xylose and lignocellulose hydrolysate, genes XYL1 and XYL2 coding for xylose reductase and xylitol dehydrogenase were overexpressed. The resulting strains exhibited increased riboflavin production in both shake flasks and bioreactors using diluted hydrolysate, reaching 1.5 g L-1.

Enhanced reducing sugar production by blending hydrolytic enzymes from Aspergillus fumigatus to improve sugarcane bagasse hydrolysis.

Biomass pretreatment for the production of second-generation (2G) ethanol and biochemical products is a challenging process. The present study investigated the synergistic efficiency of purified carboxymethyl cellulase (CMCase), ß-glucosidase, and xylanase from Aspergillus fumigatus JCM 10253 in the hydrolysis of alkaline-pretreated sugarcane bagasse (SCB). The saccharification of pretreated SCB was optimised using a combination of CMCase and ß-glucosidase (C + ß; 1:1) and addition of xylanase (C + ß + xyl; 1:1:1). Independent and dependent variables influencing enzymatic hydrolysis were investigated using response surface methodology (RSM). Hydrolysis using purified CMCase and ß-glucosidase achieved yields of 18.72 mg/mL glucose and 6.98 mg/mL xylose. Incorporation of xylanase in saccharification increased the titres of glucose (22.83 mg/mL) and xylose (9.54 mg/mL). Furthermore, characterisation of SCB biomass by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy respectively confirmed efficient structural disintegration and revealed the degree of crystallinity and spectral characteristics. Therefore, depolymerisation of lignin to produce high-value chemicals is essential for sustainable and competitive biorefinery development.

Recombinant GH3 ß-glucosidase stimulated by xylose and tolerant to furfural and 5-hydroxymethylfurfural obtained from Aspergillus nidulans.

The ß-glucosidase gene from Aspergillus nidulans FGSC A4 was cloned and overexpressed in the A. nidulans A773. The resulting purified ß-glucosidase, named AnGH3, is a monomeric enzyme with a molecular weight of approximately 80 kDa, as confirmed by SDS-PAGE. Circular dichroism further validated its unique canonical barrel fold (ß/α), a feature also observed in the 3D homology model of AnGH3. The most striking aspect of this recombinant enzyme is its robustness, as it retained 100% activity after 24 h of incubation at 45 and 50 ºC and pH 6.0. Even at 55 °C, it maintained 72% of its enzymatic activity after 6 h of incubation at the same pH. The kinetic parameters Vmax, KM, and Kcat/KM for ρ-nitrophenyl-ß-D-glucopyranoside (ρNPG) and cellobiose were also determined. Using ρNPG, the enzyme demonstrated a Vmax of 212 U mg - 1, KM of 0.0607 mmol L - 1, and Kcat/KM of 4521 mmol L - 1 s - 1 when incubated at pH 6.0 and 65 °C. The KM, Vmax, and Kcat/KM using cellobiose were 2.7 mmol L - 1, 57 U mg - 1, and 27 mmol -1 s - 1, respectively. AnGH3 activity was significantly enhanced by xylose and ethanol at concentrations up to 1.5 mol L - 1 and 25%, respectively. Even in challenging conditions, at 65 °C and pH 6.0, the enzyme maintained its activity, retaining 100% and 70% of its initial activity in the presence of 200 mmol L - 1 furfural and 5-hydroxymethylfurfural (HMF), respectively. The potential of this enzyme was further demonstrated by its application in the saccharification of the forage grass Panicum maximum, where it led to a 48% increase in glucose release after 24 h. These unique characteristics, including high catalytic performance, good thermal stability in hydrolysis temperature, and tolerance to elevated concentrations of ethanol, D-xylose, furfural, and HMF, position this recombinant enzyme as a promising tool in the hydrolysis of lignocellulosic biomass as part of an efficient multi-enzyme cocktail, thereby opening new avenues in the field of biotechnology and enzymology.

The metal cofactor: stationary or mobile?

Metal cofactors are essential for catalysis and enable countless conversions in nature. Interestingly, the metal cofactor is not always static but mobile with movements of more than 4 Å. These movements of the metal can have different functions. In the case of the xylose isomerase and medium-chain dehydrogenases, it clearly serves a catalytic purpose. The metal cofactor moves during substrate activation and even during the catalytic turnover. On the other hand, in class II aldolases, the enzymes display resting states and active states depending on the movement of the catalytic metal cofactor. This movement is caused by substrate docking, causing the metal cofactor to take the position essential for catalysis. As these metal movements are found in structurally and mechanistically unrelated enzymes, it has to be expected that this metal movement is more common than currently perceived. KEY POINTS: • Metal ions are essential cofactors that can move during catalysis. • In class II aldolases, the metal cofactors can reside in a resting state and an active state. • In MDR, the movement of the metal cofactor is essential for substrate docking.

Exploring xylose metabolism in non-conventional yeasts: kinetic characterization and product accumulation under different aeration conditions.

d-Xylose is a metabolizable carbon source for several non-Saccharomyces species, but not for native strains of S. cerevisiae. For the potential application of xylose-assimilating yeasts in biotechnological processes, a deeper understanding of pentose catabolism is needed. This work aimed to investigate the traits behind xylose utilization in diverse yeast species. The performance of 9 selected xylose-metabolizing yeast strains was evaluated and compared across 3 oxygenation conditions. Oxygenation diversely impacted growth, xylose consumption, and product accumulation. Xylose utilization by ethanol-producing species such as Spathaspora passalidarum and Scheffersomyces stipitis was less affected by oxygen restriction compared with other xylitol-accumulating species such as Meyerozyma guilliermondii, Naganishia liquefaciens, and Yamadazyma sp., for which increased aeration stimulated xylose assimilation considerably. Spathaspora passalidarum exhibited superior conversion of xylose to ethanol and showed the fastest growth and xylose consumption in all 3 conditions. By performing assays under identical conditions for all selected yeasts, we minimize bias in comparisons, providing valuable insight into xylose metabolism and facilitating the development of robust bioprocesses. ONE-SENTENCE SUMMARY: This work aims to expand the knowledge of xylose utilization in different yeast species, with a focus on how oxygenation impacts xylose assimilation.

[Construction and culture condition optimization of a Saccharomyces cerevisiae strain for production of galactitol].

Galactitol, a rare sugar alcohol, has promising potential in the food industry and pharmaceutical field. The available industrial production methods rely on harsh hydrogenation processes, which incur high costs and environmental concerns. It is urgent to develop environmentally friendly and efficient biosynthesis technologies. In this study, a xylose reductase named AnXR derived from Aspergillus niger CBS 513.88 was identified and characterized for the enzymatic properties. AnXR exhibited the highest activity at 25 ℃ and pH 8.0, and it belonged to the NADPH-dependent aldose reductase family. To engineer a strain for galactitol production, we deleted the galactokinase (GAL1) gene in Saccharomyes cerevisiae by using the recombinant gene technology, which significantly reduced the metabolic utilization of D-galactose by host cells. Subsequently, we introduced the gene encoding AnXR into this modified strain, creating an engineered strain capable of catalyzing the conversion of D-galactose into galactitol. Furthermore, we optimized the whole-cell catalysis conditions for the engineered strain, which achieved a maximum galactitol yield of 12.10 g/L. Finally, we tested the reduction ability of the strain for other monosaccharides and discovered that it could produce functional sugar alcohols such as xylitol and arabinitol. The engineered strain demonstrates efficient biotransformation capabilities for galactitol and other functional sugar alcohols, representing a significant advancement in environmentally sustainable production practices.

Spathaspora marinasilvae sp. nov., a xylose-fermenting yeast isolated from galleries of passalid beetles and rotting wood in the Amazonian rainforest biome.

Four yeast isolates were obtained from rotting wood and galleries of passalid beetles collected in different sites of the Brazilian Amazonian Rainforest in Brazil. This yeast produces unconjugated allantoid asci each with a single elongated ascospore with curved ends. Sequence analysis of the internal transcribed spacer-5.8 S region and the D1/D2 domains of the large subunit ribosomal RNA (rRNA) gene showed that the isolates represent a novel species of the genus Spathaspora. The novel species is phylogenetically related to a subclade containing Spathaspora arborariae and Spathaspora suhii. Phylogenomic analysis based on 1884 single-copy orthologs for a set of Spathaspora species whose whole genome sequences are available confirmed that the novel species represented by strain UFMG-CM-Y285 is phylogenetically close to Sp. arborariae. The name Spathaspora marinasilvae sp. nov. is proposed to accommodate the novel species. The holotype of Sp. marinasilvae is CBS 13467 T (MycoBank 852799). The novel species was able to accumulate xylitol and produce ethanol from d-xylose, a trait of biotechnological interest common to several species of the genus Spathaspora.