Biotreatment of Melanoidin-Containing Distillery Spent Wash Effluent by Free and Immobilized Aspergillus oryzae MTCC 7691

Abstract

A total of three fungal isolates from samples collected at spent wash disposal area were screened for their ability to degrade melanoidin. Distillery molasses spent wash was decolorized, and its chemical oxygen demand (COD) was reduced in immobilized fungal bioreactor (IFB) in the absence of carbon and nitrogen source using fungal mycelia of Aspergillus oryzae MTCC 7691. Fungal mycelia immobilized on baggase packed in a glass column under a batch-wise mode (1) effected removal of 75.71 ± 0.12 % color, 51.0 ± 0.13 % biological oxygen demand (BOD), 86.19 ± 2.56 % COD, and 49.0 ± 0.12 % phenolic pigments of distillery spent wash up to 25 days at 30 °C, while free fungal mycelia resulted in removal of 63.1 ± 0.16 % color, 27.74 ± 0.14 % BOD, 76.21 ± 1.62 % COD, and 37.32 ± 0.17 % phenolic pigments of distillery spent wash using shake flask, (2) manganese peroxidase (MnP) activity was highest (1.55 ± 0.01 U ml−1 min−1) in immobilized fungi, followed by lignin peroxidase (0.65 ± 0.01 U ml−1 min−1) and laccase activity (0.9 ± 0.01 CU ml−1 min−1), (3) accumulative MnP activity was highly correlated with (r = 0.9216) spent wash decolorization and (r = 0.7282) reduction of phenolic pigments, suggesting the presence of MnP activities in bioremediation of spent wash and (4) degradation of spent wash was confirmed by high-performance thin layer chromatography and gas chromatography–mass spectrometry analysis. Measurement of chlorophyll a content of Chlorella species cultivated on treated spent wash effluent obtained from immobilized fungal bioreactor was 5.16 ± 0.71 μg ml−1 compared with 1.306 ± 0.017 μg ml−1 obtained with untreated spent wash. Thus, this work may provide a reasonable alternative for cost-effective bioremediation of distillery spent wash using immobilized A. oryzae on baggase fibers.