To reduce pollution and cost of treatment for fresh and recycled paper, co-production of xylanase and laccase was carried out in the same production medium using two compatible species of Bacillus. These co-produced enzymes were used for deinking of old newsprint (ONP) and biobleaching of eucalyptus Kraft pulp. Solid-state co-cultivation of Bacillus sp. and B. halodurans FNP135 was optimized statistically by response surface methodology for the co-production of xylanase (X) and laccase (L). A significant increase in production of xylanase (2.1-fold, 1,685 IU/g) and laccase (2.04-fold, 2,270 nkat/g) was observed under optimized conditions viz. pH (10.5), inoculum size (10 + 10 %) and moisture:substrate ratio (0.8:1). Both the enzymes showed identical temperature and pH optima of 70 °C and 9, respectively, and were used for deinking of ONP pulp and biobleaching of kraft pulp. In case of ONP pulp deinking, the XL treatment increased brightness (11.8 %), freeness (17.8 %), breaking length (34.8 %), burst factor (2.77 %) and tear factor (2.4 %). In case of kraft pulp biobleaching, XL treatment showed a significant increase in brightness (13 %), whiteness (106.15 %) breaking length (49 %), burst factor (6.9 %), tear factor (23 %), and viscosity (11.68 %) and reduction in kappa number (15 %) after alkali extraction and peroxide stage. This enhancement of pulp properties revealed a synergistic effect of xylanase and laccase produced in one setup.

BackgroundThe development in the deinking process has made recycled fiber a major part of the raw material for pulp and paper industry. Enzymes have revolutionized the deinking process obtaining brightness levels surpassing conventional deinking processes. This study explores the deinking efficiencies of bacterial alkalophilic laccase (L) and xylanase (X) enzymes along with physical deinking methods of microwaving (MW) and sonication (S) for recycling of old newsprint (ONP).Methods and ResultsThe operational parameters viz. enzyme dose, pH and treatment time for X and L deinking were optimized statistically using Response Surface Methodology. Laccase did not require any mediator supplementation for deinking. Deinking of ONP pulp with a combination of xylanase and laccase enzymes was investigated, and fiber surface composition and morphological changes were studied using X-ray diffraction, fourier transform infrared spectroscopy and scanning electron microscopy. Compared to the pulp deinked with xylanase (47.9%) or laccase (62.2%) individually, the percentage reduction of effective residual ink concentration (ERIC) was higher for the combined xylanase/laccase-deinked pulp (65.8%). An increase in brightness (21.6%), breaking length (16.5%), burst factor (4.2%) tear factor (6.9%), viscosity (13%) and cellulose crystallinity (10.3%) along with decrease in kappa number (22%) and chemical consumption (50%) were also observed. Surface appeared more fibrillar along with changes in surface functional groups. A combination of physical and enzymatic processes (S-MW-XL) for deinking further improved brightness (28.8%) and decreased ERIC (73.9%) substantially.ConclusionThis is the first report on deinking of ONP with laccase without any mediator supplementation. XL pretreatment resulted in marked improvement in paper quality and a new sequence being reported for deinking (S-MW-XL) will contribute further in decreasing chemical consumption and making the process commercially feasible.

Laccases have potential applications in industrial, biotechnological, and environmental set ups. Development of cost effective and efficient production technologies has gained significant attention in recent years. To enhance the laccase production from Rheinheimera sp. (Gram negative) using submerged fermentation (SmF) and from Lysinibacillus sp. (Gram positive) using solid-state fermentation (SSF), the inducing effect of various flavonoid-rich agro-industrial residues was investigated. Peels of citrus fruits, soybean meal, tofu dreg, lignin monomers, and lingo-cellulosic waste, used tea leaves and peels of onion and kiwi, paper, and dying industry effluents were tested as inducers. In SmF, 0.1% of soybean meal, tofu dreg, and powdered orange peel were best, enhancing the laccase production 2.57-, 2.11-, and 2.05-fold, respectively. In SSF, 10 mg (w/w) of used tata acti green tea leaves per 5 g of wheat bran, 1% pulp and paper industry effluent (agro based), and 1% wine made from Sygium cumini enhanced the laccase production 2.69-, 2.61-, and 2.09-fold, respectively. These results suggest the utilization of these flavonoid and phenolic-rich waste materials to be potential enhancers of industrially important laccase production.

Bacterial diversity of hot springs of northern Himalayan region of India was studied and explored for laccases, the multicopper enzymes applicable in a large number of industries due to their ability to utilize a wide range of substrates. 220 operational taxonomic units (OTUs) out of 5551 sequence reads for bacterial diversity and 3 OTUs out of 19 sequence reads for Laccase like multicopper oxidases (LMCOs) diversity were generated. Bacteroidetes (74.28%) was the most abundant phylum including genus (66.96%), followed by phylum Proteobacteria (24.53%) including genera (7.55%) and (6.14%). In case of laccase diversity, three LMCO sequences showed affiliation with proteobacteria and one with two domain laccase from uncultivable bacteroidetes. LMCO sequences belonged to H and N families.

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