Judicial utilization of various low-cost agro-industrial wastes and optimization of various process parameters can reduce production costs of enzymes. Wheat bran was found to be the best carbon source among various agro-industrial wastes explored for Penicillium citrinum NCIM-1398. Additionally, ammonium sulphate was found as the optimum nitrogen source at moisture content 70%, pH 5.5, and temperature 30 °C for enzyme production. The maximal enzyme activities of endo β-1,4-glucanase, xylanase, FPase, and amylase were 21.0 IU/gds, 3140 IU/gds, 3.59 FPU/gds, and 73.4 IU/gds, respectively. Bio-deinking of mixed office waste paper improved the pulp brightness by 9.5%, and the effective residual ink concentration were decreased by 26.3% in comparison to MOW after pulping. Similarly, dirt counts were reduced from 4880 to1360 ppm at an enzyme dose of 6.0 IU/g compared to deinking without enzyme. The strength properties of enzymatically deinked pulp such as tear index, tensile index, and burst index increased by 6.92%, 11.31%, and 7.61%, respectively, compared with the control.

Penicillium citrinum NCIM-1398 is a co-producer of endo β-1,4-glucanase, xylanase, and amylase enzymes. The synergistic effect of the enzymes present in the cocktail was found to be advantageous in deinking white mixed office waste (MOW) paper. Enzymatic deinking of MOW reduced the dependence on chemicals by up to 50% during chemical deinking and improved optical properties compared with the chemical deinking process. The chemi-enzymatic approach improved pulp brightness by 12.6% compared with MOW pulp. The ERIC (Effective residual ink concentration) value was reduced by up to 39.2%, whereas the strength properties of tear index, tensile index, and burst index achieved gains of 3.2%, 9.9%, and 6.2%, respectively, compared with the control. Whereas chemi-enzymatic treatment showed a reduction of 67.1% in COD and 61.8% in BOD, and there was an increase of 15.4% in total solid of effluents respectively, compared with the respective controls. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) studies revealed that the pulp was modified by enzymatic and chemi-enzymatic treatments, which facilitate ink removal during deinking of pulp.

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Mixed office waste (MOW) pulp was biodeinked with crude enzyme extracted from Penicillium citrinum NCIM-1398. Crude enzyme dose was charged having activities of endo β-1,4-glucanase 6I U/g, xylanase 876.19 IU/g, and amylase 26.53 IU/g. The present study aimed to bleach the biodeinked MOW pulp with 3% H2O2 in the presence of a stabilizing agent viz. 0.1% ethylenediaminetetraacetic acid (EDTA) and 0.1% magnesium sulfate (MgSO4), which improved the pulp brightness up to 4.2% and the ERIC value was reduced by 24.1%. The residual H2O2 left in the pulp slurry after bleaching was subjected to peroxidase treatment using enzyme dose 0.017 U/g at 20 °C for 3 h at 200 rpm. Horseradish peroxidase reduced residual H2O2 in the pulp slurry from 0.30 to 0.05 g/L and improved the brightness of pulp to 88.1%, while the ERIC value was reduced by 20.9%. Potato peroxidase reduced residual H2O2 from 0.30 to 0.04 g/L, reduced the ERIC value by 30.9%, and improved the brightness to 89.2%. Peroxidase treatment was not only observed to consume the residual hydrogen peroxide left after the bleaching stage but also may come up as eco-friendly technology to recycle MOW paper as writing printing grade paper.

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