## 3 Results and Discussion  
In a previous study we reported that _P. betulinus_ IEBL-3 has a very good potential of biodegradation of vat textile dyes [17]. Vat dyes are a group of textile dyes named such because of the use of a bucket or vat during their dyeing process during the old times. It gave 66-70% and 47-59% biodegradation of vat and disperse textile dyes, respectively,after initial screening experiments. The biodegradation of vat dyes was enhanced above 80% after the optimization of conditions by using _P. betulinus_ IEBL-3. Considering the previous results, in the current study this fungus was used for the biodegradation of three different untreated textile effluents, Mujahid Textiles (MT), Sitara Textiles (ST) and Five Star Textiles (FST). **Optimization of physical parameter for biodegradation:** The process of biodegradation depends on the fungal growth in the mixture which is dependent on various physical parameters including pH, temperature, time period, dye concentration and fungal inoculum size. The effect of all five parameters on the biodegradation of three effluents was checked by employing RSM. The results obtained were used to generate the 3D graphs, showing the influence of every parameter on biodegradation and also the interaction of these parameters with each other during the process. The results showed that 76.20 \(\pm\) 1.4% biodegradation of MT effluent was obtained at pH 5.2, a time period of 08 days, a size of inoculum 6.40 mL, temperature 26.90 \({}^{\circ}\)C and dye concentration 0.04%. There was positive interaction between all the parameters during the biodegradation process as indicated by the 3D response surface graphs (Figure 1) [15]. The significant effect of these parameters on the biodegradation process was confirmed by statistical analysis and indicated by low \(p\) value (\(p\) > 0.001), high F. ratio (26.48) and high R\({}^{2}\) value (R\({}^{2}\) = 95.7  
There was almost 72.09 \(\pm\) 1.2% biodegradation of FS industrial effluent, and the most suitable conditions were pH 5.6, time of 08 days, size of inoculum 6.60 mL, temp. 27.09 \({}^{\circ}\)C and dye concentration 0.038%. The biodegradation obtained was the combinatorial effect of all of the five parameters under study, indicated by the 3D graphs obtained from the results (Figure 2). There was a significant effect on all the parameters on the biodegradation, which was also confirmed by a low \(p\) value (\(p\) > 0.001), high F. ratio (30.86) and high R\({}^{2}\) value (R\({}^{2}\) = 96.40%) [4]. Figure 1: The 3D response surface graphs of interaction between parameters during the biodegradation of MT industrial effluent by _P. betulinus_ IEBL-3; there is positive interaction between (**a**)—pH and size of inoculum (**b**)—pH and time (**c**)—size of inoculum and temp. (**d**)—size of inoculum and dye conc. (**e**)—temp. and dye conc. (**f**)—statistical analysis (* indicate significance of value). Figure 2: _Cont._  
During the current study, there was 67.10 \(\pm\) 1.2% bio-degradation of ST industrial effluent obtained. The most favorable conditions were pH 5.4, time of 08 days, size of inoculum 6.06 mL, temperature 26.90 \({}^{\circ}\)C and dye concentration 0.04%. The analysis of 3D graphs indicated that the maximum biodegradation achieved was the result of the positive and combinatorial effect of all five parameters (Figure 3). The significant effect of all parameters on the process of biodegradation of ST effluent was confirmed by the statistical analysis and indicated by a low \(p\) value (\(p\) > 0.001), high F. ratio (32.42) and high R\({}^{2}\) value (R\({}^{2}\) = 96.50%) [3]. Figure 3: _Cont_. Figure 2: The 3D response surface graphs of the interaction between parameters during the bio-degradation of FST industrial effluent by _P. lethulins_ IEBL-3; there is positive interaction between (**a**)—pH and time (**b**)—pH and temp. (**c**)—size of inoculum and time (**d**)—size of inoculum and dye conc. (**e**)—time and dye conc. (**f**)—statistical analysis (* indicate significance of value).