Impact of the fouling mechanism on enzymatic depolymerization of xylan in different configurations of membrane reactors

• Published in: Separation and purification technology Vol. 178; pp. 154 - 162
• Main Authors: Sueb, Mohd Shafiq Mohd, Luo, Jianquan, Meyer, Anne S., Jørgensen, Henning, Pinelo, Manuel
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 07.05.2017
• Subjects: Cake layer formation; Fouling mechanism; Pore blocking; Xylan depolymerization; Pore blocking; Cake layer formation; Xylan depolymerization; Fouling mechanism
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2017.01.038

•Endo-1,4-β-xylanase and β-xylosidase degraded xylan in a 1kDa PES membrane reactor.•Endo-1,4-β-xylanase generated 1–6 DP xylo-oligomers that caused internal blocking.•β-xylosidase promoted cake layer formation that prevented further enzyme action.•Reaction with both enzymes and subsequent ultrafiltration was the optimal strategy. In order to maximize enzymatic xylan depolymerization while simultaneously purifying the resulting monosaccharide (xylose), different ultrafiltration (UF) membrane reactor configurations were evaluated. Initial results showed that the two hydrolytic enzymes required for complete depolymerization of xylan, endo-1,4-β-xylanase and β-xylosidase, promoted different types of fouling, which had a direct impact on the extent of xylan hydrolysis achieved during reaction. Endo-1,4-β-xylanase generated DP 1–6 xylo-oligomers. These products contributed to partial pore blocking of the 1kDa polysulfone membrane and caused irreversible flux loss (∼20%). The presence of β-xylosidase could not prevent deposition of xylan and xylooligomers on the UF membrane surface. Mulder’s modelling of the filtration parameters affirmed that this xylan and xylooligosaccharide deposition formed a cake layer on the membrane which hindered enzymatic attack in addition to fouling. Reaction with both enzymes followed by UF was found to be the optimal configuration, providing at least 40% higher xylan hydrolysis than the cascade configuration (involving sequential reaction with each of the enzymes separately) and the simultaneous reaction-filtration with both enzymes, respectively. This study thus confirmed that the reactor configuration has a crucial impact on the performance of both the reaction and the separation process of xylose during enzymatic xylan degradation, and that the type of fouling mechanism varies in response to the type of enzyme treatment.