Repurposing mandarin peels for catalytically robust laccase production using Achromobacter denitrificans ISO16

Mandarin peels are an abundant and underutilized waste resource rich in polysaccharides, polyphenols and other essential nutrients. It is presumed that this resource can be harnessed for microbial fermentation processes, particularly catalytically-robust laccases production. This study investigated the bio-valorization of mandarin peels through response surface methodology (RSM). The model generated facilitated the computation of interactive experimental factors (pH: 5, mandarin peels: 12.5 g/L agitation: 100 rpm, NH₄NO₃: 1 g/L) that stimulate maximum yield of laccase (136 U/mL) secreted by Achromobacter denitrificans ISO16. Consequently, ISO16 laccase demonstrated tolerance, recouping at least 77 % activity after exposure to extremes in pH, temperature, salts, cations, anions and surfactants. Moreover, it was able to decolourize up to 0.2 % w v⁻¹ (2 g/L) concentrations of synthetic dyes and correspondingly facilitate a single-loop denim biobleaching. These characteristics pose ISO16 laccase as a potential industrial biocatalyst and emphasizes the importance of optimized valorization of mandarin peels to solve environmental pollution.