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Research Articles

ScienceAsia 33 (2007): 131-135 |doi: 10.2306/scienceasia1513-1874.2007.33.131

Screening of Pectinase Producing Bacteria and Their Efficiency in Biopulping of Paper Mulberry Bark

Chawanit Sittidilokratnab, Surang Suthirawuta*, Lerluck Chitradona, Vittaya Punsuvonc, Pilanee Vaithanomsatb and Prisnar Siriachab

ABSTRACT: Screening of pectinase producing bacteria and assessment of the effectiveness for biopulping of paper mulberry bark of the pectinase of the highest producer were carried out. Pectinolytic bacteria were initially screened from 6 identified and 118 unknown isolates. Twelve strains gave positive results, including 3 of Erwinia carotovora subsp. carotovora, 2 of Erwinia chrysanthemi and 7 of Bacillus sp.. Crude pectinases were prepared from the selected strains. Then, the activity of 3 pectinase types, namely polygalacturonase (PG), pectate lyase (PAL) and pectin lyase (PL), was investigated. The results showed the highest PG production from E. chrysanthemi strain N05 (342-11) isolated from onion and highest PAL and PL production from Bacillus sp. strain N10 isolated from paper mulberry bark. Both N05 and N10 possess similar optimum conditions at pH 10.0 and 35 oC, and were stable at pH 3-12 for 30 minutes and 20-40 oC for 24 h. Furthermore, the efficiency of Bacillus sp. strain N10 pectinase in biopulping of paper mulberry bark was studied. The bark was pretreated by soaking for 24 h in distilled water, 0.5% NaOH solution, or 1.0% NaOH solution or not pretreated. Then it was incubated with 20,000, 40,000, 100,000 and 200,000 units of enzyme solution and compared to water and NH4Cl-NH4OH buffer controls. Bark without any pretreatment, which was incubated with 100,000 unit of the enzyme had the maximum level of reducing sugar released, the softest pulp and fibers that were clearly separated when observed under the scanning electron microscope. Chemical composition analysis of the pulp showed slight increases in holocellulose 5%, alpha-cellulose (2%) and hemicellulose (3%) contents, whereas lignin content decreased by 50% when compared to the nontreated bark.

KEYWORDS: Pectinase, Bacteria, Biopulping, Paper mulberry bark.

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a Department of Microbiology, Faculty of Science, Kasetsart University, 50 Phaholyothin Road, Chatuchak, Bangkok 10900, Thailand.
b Kasetsart Agricultural and Agro-Industrial Product Improvement Institute, Kasetsart University, 50 Phaholyothin Road, Chatuchak, Bangkok 10900, Thailand.
c Department of Chemistry, Faculty of Science, Kasetsart University, 50 Phaholyothin Road, Chatuchak, Bangkok 10900, Thailand.

* Corresponding author, E-mail: fscisrs@ku.ac.th

Received 5 Oct 2005, Accepted 14 Jul 2006