| Congresso Brasileiro de Microbiologia 2023 | Resumo: 446-2 | ||||
Resumo:The world's demand for biofuels, in addition to favorable climatic conditions, makes Brazil the largest producer of sugarcane. Currently, sugarcane is mainly used for the production of sugar and ethanol, and bagasse is the most abundant agricultural and industrial waste. The hemicellulose fraction of sugarcane bagasse is suitable for producing xylonic acid, resulting from D-xylose oxidation, with various applications in food, pharmaceutics, and construction industries. The assimilation of D-xylose and other substrates rich in this sugar, such as sugarcane bagasse hemicellulosic hydrolysate (SBHH), is the first step required for producing xylonic acid. The purpose of this work was to isolate and identify yeast able to use SBHH as the sole carbon source. SBHH was obtained by mixing sugarcane bagasse and sulfuric acid (1% v/v, solid: liquid ratio 1:4) in a flask for 24 hours. After being autoclaved, the liquid phase was obtained by pressing (5 ton) and adding calcium hydroxide to reach pH 5,0. SBHH was supplemented with M9 mineral solution and Agar, being used as an isolation medium with Total Reducing Sugar concentration ([TRS], g/L) adjusted at 10 g/L. Samples of soil were collected in an urban forest fragment in the central Amazon Rainforest (03°06'03"S, 59°58'28" W), then diluted in sterile distilled water (1:10) and inoculated in the isolation medium by spread plate. After 48 hours, at 28 °C, yeast and yeast-like colonies were identified and isolated in Petri dishes containing Sabouraud Agar (yeast extract 10 g/L, glucose 40 g/L). The capability of assimilating D-xylose was assessed by replica plating. The most vigorous colonies were chosen for a fermentation test in SBHH with an initial [TRS] of 68.70 g/L. For the taxonomic identification, the genomic DNA was extracted and amplified by using ITS1 and NL4, which resulted in an amplicon with about 1000 pb. Nucleotide sequences were obtained in an ABI 3500 Automatic Genetic Analyzer, edited using BioEdit (7.2.5), and analyzed in BLAST (https://blast.ncbi.nlm.nih.gov/Blast.cgi). A total of 45 colonies were isolated, and the most vigorous colony in the D-xylose assimilation test was identified as Pichia kudriavzevii (99.46% similar to the type-strain, accession number EF550222.1). The SBHH fermentation resulted in a total of 12.04 g/L of yeast biomass (dry weight), biomass yield of 0.2495 g/g, and productivity of 0.1114 g/L*h. The maximum sugar consumption was reached after 36 hours of cultivation, whereas 70.2% of the total reducing sugar was consumed. Subsequent efforts will be made to analyze the fermented broth using HPLC to elucidate the production of xylitol and/or xylonic acid. Palavras-chave: Yeasts, Pichia kudriavzevii, Sugarcane bagasse, Xylitol, Xylonic acid Agência de fomento:Fundação de Amparo a Pesquisa do Estado do Amazonas | |||||