Enzymatic hydrolysis of cellulose in a membrane bioreactor: assessment of operating conditions

Abstract

The optimization of operating conditions for cellulose hydrolysis was systemically undertaken using an ultra-scaled down membrane bioreactor based on the parameter scanning ultrafiltration apparatus. The bioconversion of cellulose saccharification was carried out with freely suspended cellulase from Aspergillus niger as the biocatalyst. The polyethersulfone ultrafiltration membranes with a molecular weight cutoff of 10 kDa were used to construct the enzymatic membrane bioreactor, with the membrane showing a complete retaining of cellulase and cellobiase. The influence of solution pH, temperature, salt (NaCl) concentration, presence of cellobiase, cellulose-to-enzyme ratio and stirring speed on reducing sugar production was examined. The results showed that the addition of an appropriate amount of NaCl or cellobiase had a positive effect on reducing sugar formation. Under the identified optimal conditions, cellulose hydrolysis in the enzymatic membrane bioreactor was tested for a long period of time up to 75 h, and both enzymes and operation conditions demonstrated good stability. Also, the activation energy (E(a)) of the enzymatic hydrolysis, with a value of 34.11 ± 1.03 kJ mol(-1), was estimated in this study. The operational and physicochemical conditions identified can help guide the design and operation of enzymatic membrane bioreactors at the industrial scale for cellulose hydrolysis.

Enzymatic hydrolysis of lignocellulosic residues and bromatological characterization for animal feed

“…Enzymatic substrates saccharification without pretreatment were performed as described by LIU et al (2011), with some modifications. Assays were performed with 2 g of SH or CSC and autoclaved for 15 min at 121°C.…”

Enzymatic hydrolysis of lignocellulosic residues and bromatological characterization for animal feed

“…Enzymatic substrates saccharification without pretreatment were performed as described by LIU et al (2011), with some modifications. Assays were performed with 2 g of SH or CSC and autoclaved for 15 min at 121°C.…”

Membrane Bioreactors: A Promising Approach to Enhanced Enzymatic Hydrolysis of Cellulose

“…The activity and stability of cellulase also depend on the microbial strain used in the enzymatic cocktail recipe [114]. Other factors that affect enzymatic activity but have received much less attention are salts and the ionic strength of the reaction medium [138]. For example, the presence of sodium ions from the sodium acetate buffer used in many studies to adjust the pH of the reaction was found to enhance endoglucanase action but suppress exoglycanase [138].…”

“…Other factors that affect enzymatic activity but have received much less attention are salts and the ionic strength of the reaction medium [138]. For example, the presence of sodium ions from the sodium acetate buffer used in many studies to adjust the pH of the reaction was found to enhance endoglucanase action but suppress exoglycanase [138]. The two effects can be balanced at a certain sodium ion concentration.…”

“…The conversion improved to approximately 90% within 1 h at 55 °C when the highest agitation speed of 1200 rpm was used. The lowest tested speed of 300 rpm resulted in a conversion of almost 80% under the same conditions [138]. This enhancement was attributed to sufficient mixing in the reaction cell, which enabled better mass transfer, as well as enhanced disruption of local product accumulation around the enzymes.…”

Enzyme catalysis coupled with artificial membranes towards process intensification in biorefinery- a review

“…Possibly, due to better mass transfer, the tubular membrane gave 10% higher average conversion than the flat-sheet membrane configuration. In another MBR (Liu et al, 2011) configuration the cellulase from Aspergi. llus 11iger was free in solution and retained in the MBR by a polyethersulfone ultrafiltration membrane.…”

Enzymatic hydrolysis of lignocellulosic residues and bromatological characterization for animal feed

“…Enzymatic substrates saccharification without pretreatment were performed as described by LIU et al (2011), with some modifications. Assays were performed with 2 g of SH or CSC and autoclaved for 15 min at 121°C.…”

Membrane Bioreactors: A Promising Approach to Enhanced Enzymatic Hydrolysis of Cellulose

“…The activity and stability of cellulase also depend on the microbial strain used in the enzymatic cocktail recipe [114]. Other factors that affect enzymatic activity but have received much less attention are salts and the ionic strength of the reaction medium [138]. For example, the presence of sodium ions from the sodium acetate buffer used in many studies to adjust the pH of the reaction was found to enhance endoglucanase action but suppress exoglycanase [138].…”

“…Other factors that affect enzymatic activity but have received much less attention are salts and the ionic strength of the reaction medium [138]. For example, the presence of sodium ions from the sodium acetate buffer used in many studies to adjust the pH of the reaction was found to enhance endoglucanase action but suppress exoglycanase [138]. The two effects can be balanced at a certain sodium ion concentration.…”

“…The conversion improved to approximately 90% within 1 h at 55 °C when the highest agitation speed of 1200 rpm was used. The lowest tested speed of 300 rpm resulted in a conversion of almost 80% under the same conditions [138]. This enhancement was attributed to sufficient mixing in the reaction cell, which enabled better mass transfer, as well as enhanced disruption of local product accumulation around the enzymes.…”

Enzyme catalysis coupled with artificial membranes towards process intensification in biorefinery- a review

“…Possibly, due to better mass transfer, the tubular membrane gave 10% higher average conversion than the flat-sheet membrane configuration. In another MBR (Liu et al, 2011) configuration the cellulase from Aspergi. llus 11iger was free in solution and retained in the MBR by a polyethersulfone ultrafiltration membrane.…”

Enzymatic hydrolysis of lignocellulosic residues and bromatological characterization for animal feed

“…Enzymatic substrates saccharification without pretreatment were performed as described by LIU et al (2011), with some modifications. Assays were performed with 2 g of SH or CSC and autoclaved for 15 min at 121°C.…”

Membrane Bioreactors: A Promising Approach to Enhanced Enzymatic Hydrolysis of Cellulose

“…The activity and stability of cellulase also depend on the microbial strain used in the enzymatic cocktail recipe [114]. Other factors that affect enzymatic activity but have received much less attention are salts and the ionic strength of the reaction medium [138]. For example, the presence of sodium ions from the sodium acetate buffer used in many studies to adjust the pH of the reaction was found to enhance endoglucanase action but suppress exoglycanase [138].…”

“…Other factors that affect enzymatic activity but have received much less attention are salts and the ionic strength of the reaction medium [138]. For example, the presence of sodium ions from the sodium acetate buffer used in many studies to adjust the pH of the reaction was found to enhance endoglucanase action but suppress exoglycanase [138]. The two effects can be balanced at a certain sodium ion concentration.…”

“…The conversion improved to approximately 90% within 1 h at 55 °C when the highest agitation speed of 1200 rpm was used. The lowest tested speed of 300 rpm resulted in a conversion of almost 80% under the same conditions [138]. This enhancement was attributed to sufficient mixing in the reaction cell, which enabled better mass transfer, as well as enhanced disruption of local product accumulation around the enzymes.…”

Enzyme catalysis coupled with artificial membranes towards process intensification in biorefinery- a review

“…Possibly, due to better mass transfer, the tubular membrane gave 10% higher average conversion than the flat-sheet membrane configuration. In another MBR (Liu et al, 2011) configuration the cellulase from Aspergi. llus 11iger was free in solution and retained in the MBR by a polyethersulfone ultrafiltration membrane.…”