Xylitol production and furfural consumption by a wild type Geotrichum sp

Background: Xylitol is a five carbons polyol with promising medical applications. It can be obtained from chemical D-xylose reduction or by microbial fermentation of Sugarcane Bagasse Hemicellulosic Hydrolysate. For this last process, some microbial inhibitors, as furfural, constitute severe bottleneck. In this case, the use of strains able to produce xylitol simultaneously to furfural neutralization is an interesting alternative. A wild-type strain of Geotrichum sp. was detected with this ability, and its performance in xylitol production and furfural consumption was evaluated. Furthermore, were analyzed its degradation products. Results: Geotrichum sp. produced xylitol from D-xylose fermentation with a yield of 0.44 g-g-1. Furfural was fully consumed in fermentation assay and when provided in the medium until concentration of 6 g-L-1. The furfural degradation product is not an identified molecule, presenting a molecular weight of 161 g-mol-1, an uncommon feature for the microbial metabolism of this product. Conclusion: This strain presents most remarkable potential in performing furfural consumption simultaneous to xylitol production. Subsequent efforts must be employed to establish bioprocess to simultaneous detoxification and xylitol production by Geotrichum sp.

Isolation, taxonomic identification and investigation of the biotechnological potential of wild-type Meyerozyma guilliermondii associated with amazonian termites able to ferment D-xylose / Isolamento, identificação taxonômica e investigação do potencial biotecnológico de linhagem selvagem de Meyerozyma guilliermondii fermentadora de d-xilose associada a cupins da Amazônia

A wild-type yeast that could ferment D-xylose was isolated from the abdominal content of Nasutitermes sp. collected in the Central Amazon rainforest using sugarcane bagasse hemicellulosic hydrolyzate (SBHH) as selective medium. The yeast was identified as Meyerozyma guilliermondii. Its ability to ferment D-xylose was assessed using liquid medium containing Durham tubes. A fermentometer assay showed a low ethanol yield using D-xylose as the carbon source. Cell viability after heat shock and ethanol shock was 39.8% and 56.0%, respectively. Cultivation in SBHH (pH = 5.0) showed its capability to perform saccharification of this substrate, increasing total reducing sugar concentration to 42.6%. The log phase was observed between 36 and 108 hours of cultivation with a highest specific growth rate (µMAX) of 0.10 h-1. After 120 hours, 79.5% of total reducing sugar was consumed giving a biomass yield of 0.52 g/g. The final pH of SBHH (7.6) showed that M. guilliermondii was able to neutralize the acids of this substrate. These results agree with some predictions in the early eighties, which stated that investigations about microbial content of termite guts would provide new tools for bioconversion of lignocellulosic biomass to fuels and other added-value chemicals. This work is the first report for this species associated with termites in the Amazonian habitat.

Uma levedura selvagem fermentadora de D-xilose foi isolada do conteúdo abdominal de Nasutitermes sp., coletado na Amazônia Central usando Hidrolisado Hemicelulósico de Bagaço de Cana-de-açúcar (HHCA) como meio seletivo. A levedura foi identificada como Meyerozyma guilliermondii. Sua capacidade de fermentar D-xilose foi avaliada usando meio líquido contendo tubos de Durham. O isolado demonstrou moderada tolerância ao calor e ao etanol, com viabilidade celular de 39,8% e 56,0%, respectivamente, após submetida a estes fatores limitantes. O ensaio em fermentômetro demonstrou baixo rendimento de etanol usando D-xilose como fonte de carbono. O cultivo em HHCA (pH = 5,0) demonstrou sua capacidade de executar sacarificação e neutralização deste substrato, com aumento da concentração de açúcar redutor total em 42,6% e elevação do pH para 7,6. A fase log foi observada entre 36 e 108 horas de cultivo, com máxima taxa de crescimento específico (µMAX) de 0,10 h-1. Depois de 120 horas, 79,5% do açúcar redutor total foi consumido, com rendimento de biomassa de 0,52 g/g. Estes resultados endossam as predições de alguns autores, os quais propuseram, no início dos anos 80, que a investigação da microbiota intestinal de cupins proveria novas ferramentas para utilização de biomassa lignocelulósica e seus derivados. Este trabalho é o primeiro a reportar a ocorrência de Meyerozyma guilliermondii associada a cupins da Amazônia Central.

Cultivation of Trichosporon mycotoxinivorans in sugarcane bagasse hemicellulosic hydrolyzate

Background: The yeast strain IB09 was isolated from the gut of Calosoma sp. (Carabidae, Coleoptera, Insecta) that were collected in the central Amazon rainforest. First, tolerance of the strain to ethanol and heat was tested. Then, IB09 was cultivated in a medium using sugarcane bagasse hemicellulosic hydrolyzate as a carbon source, and cell growth (OD600), specific growth rate (uMAX, h-1), biomass yield (Y B, g.g-1) and relative sugar consumption (RSC, percent) were evaluated. Taxonomic identification was determined by sequencing the ITS1 region of IB09 and comparing it to sequences obtained from the GenBank database (NCBI). Results: IB09 showed both ethanol tolerance and thermotolerance. Relative sugar consumption indicated that IB09 was able to perform saccharification of sugarcane bagasse hemicellulosic hydrolyzate, increasing the total reducing sugar concentration by approximately 50 percent. The μMAX value obtained was 0,20, indicating that cell growth was slow under the assessed conditions. Biomass yield was 0,701 g per g of consumed sugar, which is relatively high when compared with other findings in the literature. After 120 hrs of cultivation, 80,1 percent of total reducing sugar had been consumed. Sequencing of the ITS1 region identified IB09 as Trichosporon mycotoxinivorans. Conclusion: This is the first report to document this species in the central Amazon rainforest at this host. Trichosporon mycotoxinivorans has great biotechnological potential for use in the saccharification of sugarcane bagasse hemicellulosic hydrolyzate and for biomass production with this substrate as carbon source.