Cyberlindnera dasilvae sp. nov., a xylitol-producing yeast species isolated from rotting wood and frass of cerambycid larva

Six yeast isolates were obtained from rotting wood samples in Brazil and frass of a cerambycid beetle larva in French Guiana. Sequence analysis of the ITS-5.8S region and the D1/D2 domains of the large subunit rRNA gene showed that the isolates represent a novel species of Cyberlindnera. This novel species is related to Cyberlindnera japonica, Cyberlindnera xylosilytica, Candida easanensis and Candida maesa. It is heterothallic and produces asci with two or four hat-shaped ascospores. The name Cyberlindnera dasilvae sp. nov. is proposed to accommodate the novel species. The holotype of Cy. dasilvae is CBS 16129T and the designated paratype is CBS 16584. The MycoBank number is 838252. All isolates of Cy. dasilvae were able to convert xylose into xylitol with maximum xylitol production within 60 and 72 h. The isolates produced xylitol with values ranging from 12.61 to 31.79 g l−1 in yeast extract–peptone–xylose medium with 5% xylose. When the isolates were tested in sugarcane bagasse hydrolysate containing around 35–38 g l−1 d-xylose, isolate UFMG-CM-Y519 showed maximum xylitol production.

Elucidation of new xylose metabolizing pathway in Pseudomonas gessardii VXlt-16 and its correlation with xylitol production from sugarcane bagasse hydrolysate

Scientific interventions have identified lignocellulosic biomass as potential raw material for various industrial processes. However toxic byproducts released during the process result in deterioration of environment to a greater extent. Microbes can utilize these wastes for production of products of commercial value like bio-fuels, protein, organic acids and xylitol. However, high production cost and astringent operating conditions have been the major bottlenecks for its commercial production. In microbes, xylose is metabolized by xylose isomerase (XI) and xylose reductase-xylitol dehydrogenase (XR-XDH) pathways, with later having ability to transform pure xylose as well as xylose rich lignocelluloses. Efforts to find hyper producer isolates for xylitol production resulted in identification of one such isolate Pseudomonas gessardii VXlt-16 (MG770460) by 16s rDNA sequencing. Statistical optimization resulted in 7.28 folds’ increase in xylitol yield with 64.76% xylose bioconversion. Conversion of xylose to xylitol even at large scale suggests the possible application of bacterial isolate for the production of this useful product at industrial scale.

Elucidation of New Xylose Metabolizing Pathway in Pseudomonas Gessardii VXlt-16 and its Correlation with Xylitol Production from Sugarcane Bagasse Hydrolysate

Scientific interventions have identified lignocellulosic biomass as potential raw material for various industrial processes. However toxic byproducts released during the process result in deterioration of environment to a greater extent. Microbes can utilize these wastes for production of products of commercial value like bio-fuels, protein, organic acids and xylitol. However, high production cost and astringent operating conditions have been the major bottlenecks for its commercial production. In microbes, xylose is metabolized by xylose isomerase (XI) and xylose reductase-xylitol dehydrogenase (XR-XDH) pathways, with later having ability to transform pure xylose as well as xylose rich lignocelluloses. Efforts to find hyper producer isolates for xylitol production resulted in identification of one such isolate Pseudomonas gessardii VXlt-16 (MG770460) by 16s rDNA sequencing. Statistical optimization resulted in 7.28 folds’ increase in xylitol yield with 64.76% xylose bioconversion. Conversion of xylose to xylitol even at large scale suggests the possible application of bacterial isolate for the production of this useful product at industrial scale.

Engineering Zymomonas mobilis for the Production of Xylonic Acid from Sugarcane Bagasse Hydrolysate

Sugarcane bagasse is an agricultural residue rich in xylose, which may be used as a feedstock for the production of high-value-added chemicals, such as xylonic acid, an organic acid listed as one of the top 30 value-added chemicals on a NREL report. Here, Zymomonas mobilis was engineered for the first time to produce xylonic acid from sugarcane bagasse hydrolysate. Seven coding genes for xylose dehydrogenase (XDH) were tested. The expression of XDH gene from Paraburkholderia xenovorans allowed the highest production of xylonic acid (26.17 ± 0.58 g L−1) from 50 g L−1 xylose in shake flasks, with a productivity of 1.85 ± 0.06 g L−1 h−1 and a yield of 1.04 ± 0.04 gAX/gX. Deletion of the xylose reductase gene further increased the production of xylonic acid to 56.44 ± 1.93 g L−1 from 54.27 ± 0.26 g L−1 xylose in a bioreactor. Strain performance was also evaluated in sugarcane bagasse hydrolysate as a cheap feedstock, which resulted in the production of 11.13 g L−1 xylonic acid from 10 g L−1 xylose. The results show that Z. mobilis may be regarded as a potential platform for the production of organic acids from cheap lignocellulosic biomass in the context of biorefineries.