Biobleaching of wheat straw richsoda pulp by the application of thermophilic mannanase from Bacillus sp. MG33

Thermophilic mannanase from the Bacillus sp. MG33 was applied on wheat strawrichsoda pulp to evaluate its bleaching potential. Optimum conditions for biobleaching of pulp were found as, mannanase 3Ug ¹ of pulp at pH 6.5 and temperature 65ºC that enhanced the brightness by 30% and reduced the kappa number by 20% within 2h. Tear index (1.1, points) and burst index (0.02, points) were also improved by mannanasetreated pulp as compared to the untreated pulp. Treatment of chemically (CEHIHII) bleached pulp with an enzyme showed significant effect on release of chromophores, hydrophobic and reducing compounds. Mannanaseprebleaching of raw pulp reduced the use of hypochlorite by 28% to achieve brightness of resultant hand sheets similar to the fully chemically bleached pulp. Scaning electron microscopic studies of mannanase treated pulp distinctly revealed that separation of microfibers which assist in lowering down the chemical requirement in the subsequent chemical bleaching.