RESUMEN
Xylanases are the enzymes that catalyze the breakdown of the main hemicellulose present in plant cell walls. They have attracted attention due to their biotechnological potential for the preparation of industrially interesting products from lignocellulose. While many xylanases have been characterized from bacteria and filamentous fungi, information on yeast xylanases is scarce and no yeast xylanase belonging to glycoside hydrolase (GH) family 30 has been described so far. Here, we cloned, expressed and characterized GH30 xylanase SlXyn30A from the yeast Sugiyamaella lignohabitans. The enzyme is active on glucuronoxylan (8.4 U/mg) and rhodymenan (linear ß-1,4-1,3-xylan) (3.1 U/mg) while its activity on arabinoxylan is very low (0.03 U/mg). From glucuronoxylan SlXyn30A releases a series of acidic xylooligosaccharides of general formula MeGlcA2Xyln. These products, which are typical for GH30-specific glucuronoxylanases, are subsequently shortened at the non-reducing end, from which xylobiose moieties are liberated. Xylobiohydrolase activity was also observed during the hydrolysis of various xylooligosaccharides. SlXyn30A thus expands the group of glucuronoxylanases/xylobiohydrolases which has been hitherto represented only by several fungal GH30-7 members.
Asunto(s)
Hidrolasas/metabolismo , Xilosidasas/metabolismo , Levaduras/enzimología , Secuencia de Aminoácidos , Hidrolasas/química , Homología de Secuencia de AminoácidoRESUMEN
Efficient conversion of hexoses and pentoses into value-added chemicals represents one core step for establishing economically feasible biorefineries from lignocellulosic material. While extensive research efforts have recently provided advances in the overall process performance, the quest for new microbial cell factories and novel enzymes sources is still open. As demonstrated recently the yeast Sugiyamaella lignohabitans (formerly Candida lignohabitans) represents a promising microbial cell factory for the production of organic acids from lignocellulosic hydrolysates. We report here the de novo genome assembly of S. lignohabitans using the Single Molecule Real-Time platform, with gene prediction refined by using RNA-seq. The sequencing revealed a 15.98 Mb genome, subdivided into four chromosomes. By phylogenetic analysis, Blastobotrys (Arxula) adeninivorans and Yarrowia lipolytica were found to be close relatives of S. lignohabitans Differential gene expression was evaluated in typical growth conditions on glucose and xylose and allowed a first insight into the transcriptional response of S. lignohabitans to different carbon sources and different oxygenation conditions. Novel sequences for enzymes and transporters involved in the central carbon metabolism, and therefore of potential biotechnological interest, were identified. These data open the way for a better understanding of the metabolism of S. lignohabitans and provide resources for further metabolic engineering.