Abstract
The present study originated with the concomitant production of 1.94 IU.mL-1 of pectinase, 0.34 IU.mL-1 xylanase and 0.086 IU.mL-1 cellulase from a newly isolated Bacillus firmus SDB9 in pectin salt media. Plackett-Burman Design (PBD) and Box-Behnken design (BBD) were used for optimization of mass production of pectinase using agro-residues. Statistical optimization of medium enhances the pectinase production to 17.55 IU.mL-1, 17.7% higher activity than that of unoptimized medium. The optimal pectinase activity was found at pH 8.5 and 45°C temperature. The enzyme was alkali-stable over a range of pH 7.0 to 10.0 for 1 h and thermostable at 35 to 70°C for 1h. Out of 12 tested metal cations at 1mM concentration, the enzyme was found to be hindered by the presence of three cations, whereas four cations were reported to augment, and the rest marginally subdued the activity. Pretreatment with 15 IU pectinase and 2.7 IU xylanase per gram of OD pulp reduce kappa number by 7.9%. After bleaching sequence D0-Ep-D1, the increment in pulp brightness was 2.7% with acceptable whiteness level. Pretreatment also led to a reduction in ClO2 consumption by 15% with superior brightness level. The 0.83% increase in pulp viscosity along with 3.2% gain in double fold number indicated the maintenance of relative cellulose content and strength of paper. Minor variations in burst index, tensile index and tear index reflected the conserved properties of the treated pulp. Synergistic application of mixed enzymes preparation produced from raw agro-residue headed by pectinase in preference to xylanase is first time set forth in the present study to help in cost economization and propel the pulp and paper industries towards environmental friendly future.
Highlights
The pulp and paper industry uses an immense amount of hazardous chemicals to process inordinately high quantities of raw materials for the production of virgin pulp
Based on the results of the screening a bacterial strain SDB9 which produced maximum pectinase with concurrent production of mediocre levels of xylanase and negligible cellulase activity was selected for further study
Production of pectinase from SDB9 at 72 h, 40°C and pH 8.0 on 2.5 % w/v orange peel as agricultural residue material is recommended to achieve higher yield of 16.49 IU.mL-1.Few recent discrete reports on optimization of pectinase production by Bacillus species using statistical approach are available in scientific literature that includes the screening by PBDesign and subsequent determination of optimal values of significant model terms C:N ratio, K2HPO4 and pH (Sharma and Satyanarayana, 2006).The raw substrate and abiotic parameters dominated the outcome of optimization experiments for pectinase production in Bacillus licheniformis SHG10 strains (Embaby et al, 2014)
Summary
The pulp and paper industry uses an immense amount of hazardous chemicals to process inordinately high quantities of raw materials for the production of virgin pulp. Xylanase is the key enzyme in the kraft pulp pretreatment due to its significant role in the kappa number reduction, which reflects the lignin proportion due to its better penetration as a bleaching agent after removing hexenuronic acid from the pulp (Gangwar, Prakash, & Prakash, 2014).In contrast, pectinase depolymerize polymers of galacturonic acids, and subsequently lower the cationic demand of pectin solutions and the filtrate from peroxide bleaching during paper making (Reid and Ricard, 2000; Viikari and Tenakanen, 2001). The combinatorial approach with the reverse proportion of xylanase and pectinase (where pectinase is more than xylanase) may serve as an innovative solution in kraft pulp pretreatment.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
