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Suitability of magnetic nanoparticle immobilised cellulases in enhancing enzymatic saccharification of pretreated hemp biomass.

Abraham RE, Verma ML, Barrow CJ, Puri M - Biotechnol Biofuels (2014)

Bottom Line: Cellulase from Trichoderma reesei was immobilised on an activated magnetic support by covalent binding and its activity was compared with that of the free enzyme to hydrolyse microcrystalline cellulose and hemp hurds on the basis of thermostability and reusability.The immobilised enzyme retained 50% enzyme activity up to five cycles, with thermostability at 80°C superior to that of the free enzyme.With pretreated hemp hurd biomass (HHB), the free and immobilised enzymes resulted in maximum hydrolysis in 48 h of 89% and 93%, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Chemistry and Biotechnology (CCB), Geelong Technology Precinct, Waurn Ponds, Deakin University, Geelong, Victoria 3217, Australia.

ABSTRACT

Background: Previous research focused on pretreatment of biomass, production of fermentable sugars and their consumption to produce ethanol. The main goal of the work was to economise the production process cost of fermentable sugars. Therefore, the objective of the present work was to investigate enzyme hydrolysis of microcrystalline cellulose and hemp hurds (natural cellulosic substrate) using free and immobilised enzymes. Cellulase from Trichoderma reesei was immobilised on an activated magnetic support by covalent binding and its activity was compared with that of the free enzyme to hydrolyse microcrystalline cellulose and hemp hurds on the basis of thermostability and reusability.

Results: Up to 94% protein binding was achieved during immobilisation of cellulase on nanoparticles. Successful binding was confirmed using Fourier transform infrared spectroscopy (FTIR). The free and immobilised enzymes exhibited identical pH optima (pH 4.0) and differing temperature optima at 50°C and 60°C, respectively. The K M values obtained for the free and immobilised enzymes were 0.87 mg/mL and 2.6 mg/mL respectively. The immobilised enzyme retained 50% enzyme activity up to five cycles, with thermostability at 80°C superior to that of the free enzyme. Optimum hydrolysis of carboxymethyl cellulose (CMC) with free and immobilised enzymes was 88% and 81%, respectively. With pretreated hemp hurd biomass (HHB), the free and immobilised enzymes resulted in maximum hydrolysis in 48 h of 89% and 93%, respectively.

Conclusion: The current work demonstrated the advantages delivered by immobilised enzymes by minimising the consumption of cellulase during substrate hydrolysis and making the production process of fermentable sugars economical and feasible. The activity of cellulase improved as a result of the immobilisation, which provided a better stability at higher temperatures. The immobilised enzyme provided an advantage over the free enzyme through the reusability and longer storage stability properties that were gained as a result of the immobilisation.

No MeSH data available.


Reusability study of immobilised enzyme using CMC substrate.
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Figure 6: Reusability study of immobilised enzyme using CMC substrate.

Mentions: Immobilisation of cellulase can facilitate enzyme recycling in a sequential batch-wise process, thereby lowering the enzyme cost. The immobilised enzyme was stable for up to seven consecutive cycles at 60°C of CMC hydrolysis for 30 min; thereafter, the activity reduced significantly (Figure 6). The immobilised enzymes maintained about 70% of their activity until the third cycle. Earlier studies of cellulase immobilisation on polyamidoamine (PAMAM)-grafted silica reported that 75% activity was retained after three cycles. In another study, 41% activity was retained after six cycles when the enzyme was attached using adsorption and 67% when the enzyme was covalently cross-linked [34]. Some reports have suggested that the gradual loss of enzyme activity after only a few cycles occurs due to factors such as product inhibition, structural modification of the enzyme, protein denaturation and/or inactivation of the enzyme [25]. Since the nanoparticle was magnetic in nature, it facilitated easy separation and recovery of the immobilised enzyme from the reaction mixture, thus supporting reusability.


Suitability of magnetic nanoparticle immobilised cellulases in enhancing enzymatic saccharification of pretreated hemp biomass.

Abraham RE, Verma ML, Barrow CJ, Puri M - Biotechnol Biofuels (2014)

Reusability study of immobilised enzyme using CMC substrate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4061456&req=5

Figure 6: Reusability study of immobilised enzyme using CMC substrate.
Mentions: Immobilisation of cellulase can facilitate enzyme recycling in a sequential batch-wise process, thereby lowering the enzyme cost. The immobilised enzyme was stable for up to seven consecutive cycles at 60°C of CMC hydrolysis for 30 min; thereafter, the activity reduced significantly (Figure 6). The immobilised enzymes maintained about 70% of their activity until the third cycle. Earlier studies of cellulase immobilisation on polyamidoamine (PAMAM)-grafted silica reported that 75% activity was retained after three cycles. In another study, 41% activity was retained after six cycles when the enzyme was attached using adsorption and 67% when the enzyme was covalently cross-linked [34]. Some reports have suggested that the gradual loss of enzyme activity after only a few cycles occurs due to factors such as product inhibition, structural modification of the enzyme, protein denaturation and/or inactivation of the enzyme [25]. Since the nanoparticle was magnetic in nature, it facilitated easy separation and recovery of the immobilised enzyme from the reaction mixture, thus supporting reusability.

Bottom Line: Cellulase from Trichoderma reesei was immobilised on an activated magnetic support by covalent binding and its activity was compared with that of the free enzyme to hydrolyse microcrystalline cellulose and hemp hurds on the basis of thermostability and reusability.The immobilised enzyme retained 50% enzyme activity up to five cycles, with thermostability at 80°C superior to that of the free enzyme.With pretreated hemp hurd biomass (HHB), the free and immobilised enzymes resulted in maximum hydrolysis in 48 h of 89% and 93%, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Chemistry and Biotechnology (CCB), Geelong Technology Precinct, Waurn Ponds, Deakin University, Geelong, Victoria 3217, Australia.

ABSTRACT

Background: Previous research focused on pretreatment of biomass, production of fermentable sugars and their consumption to produce ethanol. The main goal of the work was to economise the production process cost of fermentable sugars. Therefore, the objective of the present work was to investigate enzyme hydrolysis of microcrystalline cellulose and hemp hurds (natural cellulosic substrate) using free and immobilised enzymes. Cellulase from Trichoderma reesei was immobilised on an activated magnetic support by covalent binding and its activity was compared with that of the free enzyme to hydrolyse microcrystalline cellulose and hemp hurds on the basis of thermostability and reusability.

Results: Up to 94% protein binding was achieved during immobilisation of cellulase on nanoparticles. Successful binding was confirmed using Fourier transform infrared spectroscopy (FTIR). The free and immobilised enzymes exhibited identical pH optima (pH 4.0) and differing temperature optima at 50°C and 60°C, respectively. The K M values obtained for the free and immobilised enzymes were 0.87 mg/mL and 2.6 mg/mL respectively. The immobilised enzyme retained 50% enzyme activity up to five cycles, with thermostability at 80°C superior to that of the free enzyme. Optimum hydrolysis of carboxymethyl cellulose (CMC) with free and immobilised enzymes was 88% and 81%, respectively. With pretreated hemp hurd biomass (HHB), the free and immobilised enzymes resulted in maximum hydrolysis in 48 h of 89% and 93%, respectively.

Conclusion: The current work demonstrated the advantages delivered by immobilised enzymes by minimising the consumption of cellulase during substrate hydrolysis and making the production process of fermentable sugars economical and feasible. The activity of cellulase improved as a result of the immobilisation, which provided a better stability at higher temperatures. The immobilised enzyme provided an advantage over the free enzyme through the reusability and longer storage stability properties that were gained as a result of the immobilisation.

No MeSH data available.