Abstract
In the present study, crude bacterial extract containing violacein is investigated for the preparation of antimicrobial polyamide fabrics. The optimal culture conditions of Janthinobacterium lividum (JL) for maximum biomass and violacein production were found to be 25°C, pH 7.0, while the addition of ampicillin of 0.2 mg mL-1 in the small scale increased violacein production 1.3-fold. In scale-up trials, the addition of 1% (v/v) glycerol in a fed-batch bioreactor, resulted in fivefold extracted crude violacein increase with final concentration of 1.828 g L-1. Polyamide 6.6 fabrics were dyed following three different processes; through simultaneous fermentation and dyeing (SFD), by incubating the fabric in the sonicated bacterial culture after fermentation and by using cell-free extract containing violacein. Maximum color change (ΔE) and color strength (K/S) obtained for SFD fabrics were 74.81 and 22.01, respectively, while no alteration of fastness and staining of dye at acid and alkaline perspiration or at water was indicated. The dyed fabrics presented significant antifungal activity against Candida albicans, C. parapsilosis, and C. krusei, as well as antibacterial properties against Escherichia coli, Staphylococcus aureus, and the S. aureus MRSA. We have shown that J. lividum cultures can be successfully used for violacein production and for simultaneous dying of fabrics resulting in dyed fabrics with antimicrobial properties without utilization of organic solvents.
Highlights
Over the years, the production of natural pigments from different biological sources, such as bacteria, fungi, and algae has been established
Lower production of biomass was observed for pH 5.0 with no violacein production, where pH 9.0 proved a hostile environment for J. lividum prosperity
At higher temperatures of 30 and 35◦C no biomass production was noted and subsequently there was no violacein production, while at 20◦C biomass reached a concentration of 0.38 mg mL−1 with second best violacein production, justifying the psychrotrophic character of J. lividum
Summary
The production of natural pigments from different biological sources, such as bacteria, fungi, and algae has been established. While synthetic dyes of lower cost rapidly expanded in different applications including textile industry, it remains an undisputable fact that biological dyes remain a “green” solution due to their biodegradability. The biotechnological dye production through fermentation processes comprises an eco-friendly approach, without the drawbacks that the chemical synthesis of dyes present. The modification of fabrics in order to acquire antimicrobial properties and other functionalities represents a new trend because of the “superbugs” problem Turning to a biotechnological direction, fabric dyeing using biological dyes with antimicrobial properties, such as prodigiosins (Stankovic et al, 2014) or violacein, is an attractive prospective to address the arising health problem
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