The Biodegradation of Indigo Carmine by Bacillus safensis HL3 Spore and Toxicity Analysis of the Degradation Products

Abstract

The aims of this article were to investigate Bacillus safensis HL3 spore for its capacity to degrade and detoxify indigo carmine and to provide an effective biological agent for the treatment of isatin dye wastewater. Bacillus safensis HL3 spore was found to decolorize indigo carmine by 97% in the presence of acetosyringone within 2 h. Significantly increased activities of spore laccase, intracellular tyrosinase, and lignin peroxidase upon exposure to indigo carmine were observed. The results of RT–qPCR also showed that the expression of laccase gene was significantly increased. The spore has the ability to degrade indigo carmine through oxidization. Furthermore, the pathway by which indigo carmine is degraded was investigated using liquid chromatography–mass spectrometry analysis to identify the biodegradation products. A detailed pathway of indigo carmine degradation by bacterial spores was proposed for the first time. Toxicity tests indicated that the biodegradation products of indigo carmine are non-toxic to Nicotiana tabacum seeds and are less hazardous to human erythrocytes than the original dye. Indigo carmine is a typical recalcitrant dye and severely jeopardizes human health. The results demonstrate the utility of the spore from Bacillus safensis HL3 for the degradation of indigo carmine and simultaneous reduction of its toxicity.

Decolorisation of textile wastewater using biosynthesised iron oxide nanomaterials and Optimisation by Response Surface Methodology

“…Compared to the original dye, 47 mg L −1 of indigo carmine or its related breakdown products are less harmful to human erythrocytes and non‐toxic to Nicotiana tabacum seeds. The common recalcitrant dye, indigo carmine, seriously endangers the health of people [51] …”

Decolorization and Detoxification of Industrial Wastewater Containing Indigo Carmine by Aspergillus niger AN400 in Sequential Reactors

“…The still high toxicity observed after fungal treatment may be related to the formation of more toxic by-products, such as isatin, an intermediate metabolite of the biological degradation of indigo carmine, previously identified, whose final product is 2aminobenzoic acid, an aromatic amine that under the action of the laccase enzyme produced by fungi can result in free radicals that can be further degraded or polymerized [40,41]. According to Wang et al [42], the action of laccase enzymes facilitates the cleavage of the C=C bond of indigo carmine, leading to the formation of the intermediate product isatin 5-sulfonic acid. The subsequent biodegradation of this intermediate yields additional byproducts, including isatin, methanol, and 2-aminobenzaldehyde, which may possess higher toxicity levels compared to the original molecule.…”