RESUMO

Xylanolytic enzymes are involved in xylan hydrolysis, the main ones being endo-ß-1,4-xylanases (xylanases). This can be applied in the bioconversion of lignocellulosic materials into value-added products such as xylooligosaccharides (XOS). This study aimed to establish a protocol for the purification of xylanases, as well as to characterize and apply the purified enzyme extract in the production of XOS. The enzyme purification techniques studied were ammonium sulfate ((NH4)2SO4) and ethanol precipitation. Purification of xylanase by fractional precipitation (20-60%) with (NH4)2SO4 was more efficient than with ethanol because the salt precipitation reached a purification factor of 10.27-fold and an enzymatic recovery of 48.6% The purified xylanase exhibited optimum temperature and pH of 50 °C and 4.5, respectively. The Michaelis-Menten constant using beechwood xylan for the enzyme was 74.9 mg/mL. The addition of salts such as CaCl2, ZnCl2, and FeCl3 in the reaction medium increased the xylanase activity. Xylanase showed greater thermal stability (half-life = 169 h) at 45 °C and pH 4.5. Under these conditions and in the presence of Ca2+ (10 mmol/L) the enzyme was even more stable (half-life = 231 h). Total XOS contents (6.7 mg/mL) and the conversion of xylan to XOS (22.3%) between 2 and 24 h were statistically equal. The hydrolysates showed the majority composition of xylobiose, xylotriose, and xylose. The addition of Ca2+ ions did not contribute to an increase in the total XOS content or to a greater conversion of xylan into XOS, but the hydrolysate was richer in xylobiose and had a lower xylose content.

Assuntos

Endo-1,4-beta-Xilanases , Glucuronatos , Aureobasidium , Hidrólise , Oligossacarídeos , Xilanos

RESUMO

Xylooligosaccharides (XOS) are non-digestible and fermentable oligomers that stand out for their efficient production by enzymatic hydrolysis and beneficial effects on human health. This study aimed to investigate the influence of the main reaction parameters of the beechwood xylan hydrolysis using crude xylanase from Aureobasidium pullulans CCT 1261, thus achieving the maximum XOS production. The effects of temperature (40 to 50 °C), reaction time (12 to 48 h), type of agitation, substrate concentration (1 to 6%, w/v), xylanase loading (100 to 300 U/g xylan), and pH (4.0 to 6.0) on the XOS production were fully evaluated. The most suitable conditions for XOS production included orbital shaking of 180 rpm, 40 °C, and 24 h of reaction. High contents of total XOS (10.1 mg/mL) and XOS with degree of polymerization (DP) of 2-3 (9.7 mg/mL), besides to a high percentage of XOS (99.1%), were obtained at 6% (w/v) of beechwood xylan, xylanase loading of 260 U/g xylan, and pH 6.0. The establishment of the best hydrolysis conditions allowed increasing both the content of total XOS 1.5-fold and the percentage of XOS by 9.4%, when compared to the initial production (6.7 mg/mL and 89.7%, respectively). Thus, this study established an efficient enzymatic hydrolysis process that results in a hydrolysate containing XOS with potential prebiotic character (i.e., rich in XOS with DP 2-3) and low xylose amounts.

Assuntos

Glucuronatos , Oligossacarídeos

RESUMO

Bioactive compounds can provide health benefits beyond the nutritional value and are originally present or added to food matrices. However, because they are part of the food matrices, most bioactive compounds remain in agroindustrial by-products. Agro-industrial by-products are generated in large quantities throughout the food production chain and can-when not properly treated-affect the environment, the profit, and the proper and nutritional distribution of food to people. Thus, it is important to adopt processes that increase the use of these agroindustrial by-products, including biological approaches, which can enhance the extraction and obtention of bioactive compounds, which enables their application in food and pharmaceutical industries. Biological processes have several advantages compared to nonbiological processes, including the provision of extracts with high quality and bioactivity, as well as extracts that present low toxicity and environmental impact. Among biological approaches, extraction from enzymes and fermentation stand out as tools for obtaining bioactive compounds from various agro-industrial wastes. In this sense, this article provides an overview of the main bioactive components found in agroindustrial by-products and the biological strategies for their extraction. We also provide information to enhance the use of these bioactive compounds, especially for the food and pharmaceutical industries.