Recyclable Soluble–Insoluble Upper Critical Solution Temperature-type Poly(methacrylamide-co-acrylic acid)–Cellulase Biocatalyst for Hydrolysis of Cellulose into Glucose

Abstract

How to improve the accessibility of immobilized cellulase to insoluble cellulose and recover immobilized enzyme from remaining insoluble substrate is a challenge to the efficient hydrolysis of cellulose into glucose. The objective of this work is to solve the problems mentioned above by the immobilization of cellulase onto poly(methacrylamide-coacrylic acid) (PMAAc), developing a reversibly soluble− insoluble biocatalyst with upper critical solution temperature (UCST) of 16 °C. The as-prepared PMAAc−cellulase with a new UCST of 19 °C exhibited significantly improved pH, temperature, storage, and operation stabilities compared with that of free catalyst, and about 82.4% of its original activity was retained even after ten cycles. Cellulase systems containing endo-β-1,4-glucanase (EG), cellobiohydrolase (CBH), and βglucosidase (β-G) are coimmobilized at an optimum ratio on PMAAc by adjusting the additive amount of β-G, which can obtain higher hydrolysis efficiency. It was found that the coimmobilization of cellulase and β-glucosidase at the optimum ratio of 2.5:1 (w/w) showed excellent performance for the hydrolysis of cellulose, and the yield of glucose was up to 89.1% at 50 °C (>UCST) after 24 h, which was 58.4% and 15.4% higher than that of PMAAc−cellulase and free cellulase and β-glucosidase, respectively. The coimmobilized PMAAc−cellulase and β-glucosidase still retained 61.48% of its original productivity after eight cycles of hydrolysis. This novel UCST-type polymer−enzyme catalytic system displays great potential in cellulose biorefining.

Preparation of regenerable magnetic nanoparticles for cellulase immobilization: Improvement of enzymatic activity and stability

“…It has been observed that a greater amount of cellulase increases the intermolecular steric barrier and limits the reaction efficiency of the cellulase to the support 50 . Furthermore, in the literature, an excess of cellulase immobilization on the support surface will lead to steric blocking among enzymes, reducing their activity by blocking active sites 51‐53 …”

“…50 Furthermore, in the literature, an excess of cellulase immobilization on the support surface will lead to steric blocking among enzymes, reducing their activity by blocking active sites. [51][52][53] The effects of immobilization temperature and pH are also examined. As shown in Figure 8(c,d), the highest amount of cellulase loading was displayed to be pH 5 and temperature 50 C. At a higher pH, this may be caused by the destruction of the hydrogen bond, which determines the partial inactivation and support of the enzyme.…”

Strategies towards Reduction of Cellulases Consumption: Debottlenecking the Economics of Lignocellulosics Valorization Processes

“…Lignocellulosic materials fulfill some properties required in a promising support, such as large availability and low cost [86]. Finally, relevant progress in new innovative supports should also be noted such as the cases of biomimetic films [87], nanomaterials [88] and stimuli-responsive smart materials [89].…”

Advances in thermo-responsive polymers exhibiting upper critical solution temperature (UCST)

“…To solve this problem, poly(methacrylamide-co-acrylic acid) (PMAAc) with UCST of 16°C was utilized to immobilized cellulase enzyme in order to enhance the stability at high temperature and to enable easy recovery of enzyme below UCST. The hydrolysis rate of insoluble cellulose to glucose at elevated temperature was significantly enhanced with the aid of newly developed biocatalyst while retaining the enzyme activity [77].…”