Natural pigment extraction from five filamentous fungi for industrial applications and dyeing of leather

Abstract

The present study aimed to evaluate and optimize the dyeing potential of fungal pigments for pre tanned leather samples. Five different water-soluble pigments were extracted from Monascus purpureus, Isaria spp., Emericella spp., Fusarium spp. and Penicillium spp., purified and used for dyeing processes. The effect of process parameters of dyeing such as pH, temperature, time duration, exhaustion of colour, shade brightness, colour intensity and fastness properties have been studied and the conditions were optimized. The results showed that the optimum concentration of the pigments were 6% on weight of leather. However, the optimum condition for dyeing was 70 °C, at a pH 5, and the time duration 120 min. The maximum uptake of pigments in the leather samples varied from 40% to 70 ± 0.2%. The changes in shades of the samples were high in M. purpureus – red pigment and it compared with visual assessment data. The fungal pigments did not significantly alter the organoleptic properties of the leather sample.

Introduction

Highly coloured substances, known as dyes or colourants, are widely used to impart colour to a boundless variety of materials described technically as substrates (McLaren, 1983, Sivakumar et al., 2009). The increased application of these dyes or colourants in dyeing industries and inefficiencies in dyeing result in a large amount of dyestuff being directly lost in the wastewater, which ultimately finds way into the environment. It is estimated that 10–35% of the dye is lost in the effluent during the dyeing process, while in the case of reactive dyes, as much as 50% of the initial dye load is present in the dye bath effluent (Rai et al., 2005). Moreover, some of these dyes contain potential colon carcinogens, which is a possible hazard to humans when chronically exposed (Osman, Sharaf, Osman, El-Khouly, & Ahmed, 2004). Hence, there is a growing demand for eco-friendly/non-toxic colourants, specifically for health sensitive applications such as colouration of food and dyeing of child textile and leather garments.

Natural dyes and pigments are emerged as an important alternative to potentially harmful synthetic dyes (Sivakumar et al., 2009). The application of these natural dyes and pigments in dyeing of cotton, silk and wool samples has reported in several studies (Kamel et al., 2009, Rekaby et al., 2008). However, the main disadvantage of these natural dyes or pigments lies in the order of magnitude of their extraction yield factors (a few grams of pigment per kg of dried raw material). This makes their current market price about USD 1/g, thus limiting their application to high-value-added natural-coloured garments only. To defeat this constraint, it is suggested to exploit the potentiality of other biological sources such as fungi, bacteria and cell cultures, since appropriate selection, mutation or genetic engineering techniques are likely to improve significantly the pigment production yields with respect to wild organisms (Mapari et al., 2005).

Fungi are reported as potent pigment producing microorganisms (Babitha, Soccol, & Pandey, 2007). Hamlyn (1995) reported the importance of pigments such as anthraquinone, anthraquinone carboxylic acids, pre-anthraquinones extracted from filamentous fungi. The application of these fungal pigments in dyeing of cotton, silk and wool has reported in several studies (De Santis et al., 2005, Nagia and EL-Mohamedy, 2007). However, the application of these fungal pigments for leather sample has not been determined. Hence, the main objective of the present study is to develop simple methodology for both extractions of pigment from filamentous fungi as well as for application in the leather dyeing. Moreover, the dyeing conditions were optimized and characteristics of dyed leather samples were assessed by standard methods.