Full Length Research Paper

Strain improvement in dye decolourising mutants of Mucor mucedo by protoplast fusion

Bhargavi Moturi¹* and M. A. Singara Charya²

¹Centre for Biotechnology, Jawaharlal Nehru Technological University, Hyderabad – 5000085, AP, India.

²Department of Microbiology, Kakatiya University, Warangal – 506009, AP, India.

*Corresponding author. E-mail: moturi.bhargavi@yahoo.co.in.

Tel: +91 9663479559.

Accepted 5 November, 2009

   Abstract

The amounts of protoplasts obtained in the developed mutants of M. mucedo MMM₁ (U.V. irradiated mutant) and MMM₂ (ethyl methyl sulfonate treated mutant) which are very effective decolourisers were 5.23 x 10⁶ and 5.65 x 10⁶ protoplasts/ml respectively. Among the 385 colonies isolated after protoplast fusion only 3 possessed clamp connections and chosen as fusants (MMFu₁, MMFu₂ and MMFu₃). Of the 3 fusants, MMFu₃ showed maximum growth rate on potato dextrose agar plates incubated at room temperature. The fusant MMFu₃ showed very good increase in the production of three enzymes protease (1.90 U/ml), peroxidase (1100 U/ml) and laccase (200 U/ml) when compared to the two parent strains proving that the higher enzymatic secretions are responsible for the decolourisation activity. In protease isozyme analysis, fusants showed bands common to either of the parental strains or to both. Further non parental new bands were observed in the protease isozyme patterns of MMFu₃. This fact indicated that the isolates were fusants between MMM₁ and MMM₂. The fusant MMFu₃ showed the maximum decolourisation of crystal violet up to 95% and malachite green up to 84% after 10 days of incubation. The results clearly indicated that the protoplast fusants showed improvement in the decolourisation efficiency in both the cases of crystal violet and malachite green.

Key words: Protoplasts, Mucor mucedo, fusants, protease, decolourisation activity.