Cryptococcus laurentii: a wild yeast for xylanase production from agricultural by-products

The development of technologies that allow the production of enzymes at a competitive cost is of great importance for several biotechnological applications, and the use of agro-industrial by-products is an excellent alternative to minimize costs and reduce environmental impacts. This study aimed to produce endo-xylanases using agro-industrial substrates rich in hemicellulose as sources of xylan in culture media. For this purpose, the yeast Cryptococcus laurentti and five lignocellulosic materials (defatted rice bran, rice husk, corn cob, oat husks, and soybean tegument), with and without pretreatment, were used as a source of xylan for enzyme production. To insert the by-products in the culture medium, they were dried and treated (if applicable) with 4% (w.v^-1) NaOH and then added in a concentration of 2% (w.v^-1). The cultures were agitated for 96 h, and the aliquots were removed to determine the enzymatic activities. Among the by-products studied, the maximum activity (8.7 U. mL^-1 at pH 7.3) was obtained where rice bran was used. In contrast, corn cob was the by-product that resulted in lower enzyme production (1.6 U.mL^-1). Thus, the defatted rice bran deserves special attention in front of the other by-products used since it provides the necessary substrate for producing endo-xylanases by yeast.