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.

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RESUMO

A perda de tecido duro, ou seja a desmineralização do dente, na região cervical , não associada à cárie, define um grupo de lesões conhecidas como lesões dentárias de origem não cariosa (LDNC). A etiologia das LDNC é considerada multifatorial. Foi proposto que elas se iniciam devido à incidência de forças oclusais cíclicas fora do longo eixo do dente, que causam sua deflexão. Foi encontrada associação entre a presença de LDNC e fatores oclusais como trauma oclusal e facetas de desgaste, o que justifica um acurado exame oclusal do paciente com essas lesões. Devido às dificuldades do clínico em diagnosticar as características oclusais associadas às LDNC, este trabalho tem por objetivo estabelecer um protocolo de exame clínico auxiliar de diagnóstico utilizando um relato de caso clínico como referência. Aos exames extra e intra-orais, verificou-se o tipo de oclusão dentária e suas possíveis relações com as LDNC encontradas, e se quantificou a influência de fatores de risco como consumo de substância ácida, bebidas gaseificadas, fatores ambientais, agentes etiológicos intrínsecos e a oclusão. O protocolo mostrou-se uma ferramenta eficaz para ajudar o clínico e facilitar o diagnóstico das possíveis etiologias das LDNC...

The loss of hard tissue, or desmineralizatio of teeth, in the cervical region, not associated with caries, defines a group of lesions known as non carious dental lesion (NCDL). The etiology of NCDL is considered multifactorial. It has been proposed that they are initiated due to the effect of cyclic occlusal forces outside the long axis of the tooth, which cause its deflection. Association was found between the presence of NCDL and occlusal factors as occlusal trauma and wear facets, which justifies an accurate occlusal examination of patients with these lesions. Considering the difficulties of diagnosing clinical occlusal characteristics associated with NCDL, this work aimed to establish a clinical examination protocol diagnostic aid using a case report as a reference. During extra and intra-oral examinations wasidentified the type of dental occlusion and its possible relations with NCDL, and quantified the influence of risk factors such as consumption of acidic substance, carbonated drink, environmental factors, intrinsic etiologic agents, and occlusion. The proved to be an effective tool to help the clinician and facilitate the diagnosis of possible etiologies of NCDL...

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