Growth of wood-inhabiting yeasts of the Faroe Islands in the presence of spent sulphite liquor

In the microbial community of decaying wood, yeasts are important for the recycling of nutrients. Nevertheless, information on their biodiversity in this niche in the Northern hemisphere is limited. Wood-colonising yeasts encounter identical and similar growth-inhibitory compounds as those in spent sulphite liquor (SSL), an energy-rich, acid hydrolysate and waste product from the paper industry, which may render them well-suited for cultivation in SSL. In the present study, yeasts were isolated from decaying wood on the Faroe Islands and identified based on sequence homology of the ITS and D1/D2 regions. Among the yeasts isolated, Candida argentea, Cystofilobasidium infirmominiatum, Naganishia albidosimilis, Naganishia onofrii, Holtermanniella takashimae and Goffeauzyma gastrica were new to decaying wood in cold and temperate climates. C. argentea and Rhodotorula are rarely-isolated species, with no previous documentation from cold and maritime climates. The isolates were further tested for growth in a medium with increasing concentrations of softwood SSL. Most grew in the presence of 10% SSL. Isolates of Debaryomyces sp., C. argentea and Rhodotorula sp. were the most tolerant. Representatives of Debaryomyces and Rhodotorula have previously been found in decaying wood. In contrast, the least tolerant isolates belonged to species that are rarely reported from decaying wood. The relative importance of individual inhibitors to yeast growth is discussed. To our knowledge, none of the present yeast species have previously been cultivated in SSL medium. Decaying wood can be a useful future source of yeasts for valorisation of various hydrolysates to industrial chemicals and biofuels.

Production of Xanthan Gum by Xanthomonas Campestris CCT 13951 Submerged Fermentation on hydrolysed agroindustrial by-products

Xanthan is a natural polymer often obtained through fermentative processes using Xanthomonas, which remarkable properties - including biocompatibility, biodegradability, and non-toxicity – fit a myriad of industrial applications. The aim of this study was to evaluate the influence of different alternative fermentable substrates derived from agro-industrial waste (cheese whey and passion fruit peel), the production and rheological properties of the gum. The fermented substrate composition had a strong impact on production (8.15–14.81 g∙L-1) and apparent viscosity (31.9–510 mPa.s). The maximum xanthan gum production was observed after 72 h using cheese whey and passion fruit peel acid hydrolysate supplemented with K2HPO4 (AH:W – Phosphate). However, the maximum viscosity was found for medium without supplementation (AH:W), twice the value of the samples supplemented with phosphate. All solutions were highly pseudoplastic. This study provides a cost-effective solution for the reusing of cheese whey and passion fruit peel and possible low-cost approach for xanthan production. .

Fast Measurement of Lipid Content of Oleaginous Yeast Trichosporon dermatis Cultured in Lignocellulosic Hydrolysates Using Fluorescent Method

To avoid complex procedures in measurement of lipid content of oleaginous yeast especially for that can accumulate microbial lipid in lignocellulosic hydrolysates, fluorescent method using Nile Red as fluorescent dye was applied to measure lipid content of oleaginous yeast Trichosporon dermatis. The fluorescent method was built by fitting of lipid content identified by both conventional gravimetric method and fluorescence intensity of oleaginous yeast. Within the range of lipid content measured, the fitting curves showed linear relationship with good correlation coefficient (R2=0.95), showing this method is suitable for measuring lipid content of T. dermatis in the simulated medium. To evaluate the applicability of this method for lipid fermentation using lignocellulosic acid hydrolysates as substrate, T. dermatis was cultured in corncob acid hydrolysate and rice straw acid hydrolysate and then its lipid content measured by both fluorescent method and gravimetric method were compared. The results showed that the lipid content measured by these two methods were close, therefore, this method was promising for the application in lipid fermentation in lignocellulosic acid hydrolysates.

Fast Measurement of Lipid Content of Oleaginous Yeast Trichosporon dermatis Cultured in Lignocellulosic Hydrolysates Using Fluorescent Method

To avoid complex procedures in measurement of lipid content of oleaginous yeast especially for that can accumulate microbial lipid in lignocellulosic hydrolysates, fluorescent method using Nile Red as fluorescent dye was applied to measure lipid content of oleaginous yeast Trichosporon dermatis. The fluorescent method was built by fitting of lipid content identified by both conventional gravimetric method and fluorescence intensity of oleaginous yeast. Within the range of lipid content measured, the fitting curves showed linear relationship with good correlation coefficient (R2=0.95), showing this method is suitable for measuring lipid content of T. dermatis in the simulated medium. To evaluate the applicability of this method for lipid fermentation using lignocellulosic acid hydrolysates as substrate, T. dermatis was cultured in corncob acid hydrolysate and rice straw acid hydrolysate and then its lipid content measured by both fluorescent method and gravimetric method were compared. The results showed that the lipid content measured by these two methods were close, therefore, this method was promising for the application in lipid fermentation in lignocellulosic acid hydrolysates.