BIOSORPTION OF REACTIVE BLACK B BY DRIED FUNGAL BIOMASS

* Nishant junnarkar 1,2 and neepa pandhi 1 . 1. Department of Microbiology, Shree M. & N. Virani Science College, Rajkot, Gujarat, India. 360005. 2. School of Life Sciences, Central University of Gujarat, Gandhinagar, Gujarat, India. 382030. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

Biosorption of Reactive Black B (RBB) dye was attempted with dried biomass of P. chrysosporium MTCC 787, Aspergillus sp. WRF3 and Trichoderma sp. WG1. Effect of biosorbent dosage, pH and contact time on biosorption of RBB was assessed. All the three cultures were observed to have high potential for the removal of RBB even at low biosorbent dosage. Acidic pH was more suitable for biosorption of RBB from the solution and 7h contact time was needed for maximal removal of dye (>90%) from the dye solution at 3gL -1 biosorbent dosage. Thus, these cultures can be useful in biosorptive removal of RBB containing wastewaters.
The uptake or accumulation of chemicals by biomass has been termed biosorption (Tsezos and Bell, 1989;Hu 1992Hu , 1996Kumar et al., 1998). Dead bacteria, yeast and fungi have all been used for the purpose of decolorizing dyecontaining effluents. Textile dyes vary greatly in their chemistries, and therefore their interactions with microorganisms depend on the chemistry of a particular dye and the specific chemistry of the microbial biomass (Polman and Brekenridge, 1996). Depending on the dye and the species of micro-organism used different binding rates and capacities are observed. It can be said that certain dyes have a particular affinity for binding with microbial species.

Materials and Methods:-
Organisms:-Phaenerochaete chrysosporium MTCC 787 was procured from Institute of Microbial Technology (IMTECH), Chandigarh, India. It was routinely subcultured on Malt Extract Agar (MEA, Himedia) medium and preserved at 4ºC on MEA slants till further use. Fungal strains WRF3 and WG1 were isolated from the soil samples collected from Atmiya Campus, Rajkot; which were also routinely sub-cultured on MEA medium and preserved at 4ºC on MEA slants.

941
Bavendam's test:-0.1 mL of fungal spore suspension, prepared in sterile distilled water containing Tween 80 (0.05% v/v) was spread on MEA medium supplemented with tannic acid (0.1%, w/v). The plates were incubated at 30˚C and were observed for changes in the color of the medium.
Isolation and screening of white rot fungi:-Soil samples collected from the garden at Atmiya Group of Institutions Campus (22º 17'11.6"N, 70º46'22.6" E), Rajkot, Gujarat, India; were suspended in sterile distilled water at the rate of 1% (w/v), from which 0.1 mL of the supernatant was spread on the Malt Extract Agar medium and incubated at 28ºC. The fungal colonies were successively transferred to obtain pure cultures, which were then subjected to Bavendam's test, to assess their ability to bleach tannic acid containing medium (a test used to screen white rot fungi).
After 7d entire contents of the flasks were filtered out individually and fungal biomass of each culture was washed with distilled water, which was then subjected to drying in oven at 35°C. Dried biomass of each fungal culture was then finely ground using mortar and pestle and was used as biosorbent for the biosorptive removal of dye from the 50 ppm solution of Reactive Black B.

Effect of biosorbent dosage:-
To study the effect of sorbent dosage, varying concentration of dried biomass (0.2-5g/L) was added in 20 mL RBB solution (50ppm, pH 7) contained in 50 mL flask. All the flasks were placed on orbital shaker (100rpm) for 5h at 30ºC. After 5h, the contents of the flask were filtered and decolorization rate was reported using the formula mentioned below. Experimental sets were run in triplicate.

Effect of pH on biosorption of dye:-
Effect of pH was studied using 50 ppm RBB solution prepared in different buffers (0.1M), listed in Table 4.1. Biosorbent dosage was kept to 3gL -1 in each flask. For each pH, experimental sets were run in triplicates.  Fig.  1a and 1b respectively. However, for convenience Aspergillus sp. WRF3 is referred as WRF3 and Trichoderma sp. WG1 is referred as WG1, further in this paper.

Biosorption of RBB by dried biomass of P. chrysosporium, WRF3 and WG1:-
Finely powdered dry biomass of fungal cultures P. chrysosporium, WRF3 and WG1 was individually tested as biosorbent for the biosorptive removal of RBB dye at 50 ppm concentration under shaking conditions. Different parameters viz. effect of biosorbent dosage, effect of pH on biosorption of RBB and effect of contact time on biosorption of RBB were tested.

Effect of biosorbent dosage on biosorptive removal of RBB:-
The effect of biosorbent dosage on decolorization rate of RBB under shaking conditions is shown in Fig. 2. Here, as biosorbent dosage increased, decolorization rate also increased. Increase in the decolorization rate may be attributed to the availability of more adsorption sites on biosorbent surface at higher dosage, for binding by the dye molecule. Similar observations were reported by Khalaf (2008) for biosorption of reactive dyes Synazol Red HF6BN and Syanazol Yellow HF2GR by inactivated biomass of Aspergillus niger and Spirogyra sp. At higher biomass concentration, there is a very fast superficial biosorption onto the cell that produces a lower solute concentration in the solution than when cell concentration is lower (Donmez et al., 1999). There are marked differences in the structure and composition of the cell wall of fungi from diverse groups (Deacon, 2006). Gupta et al. (2000) suggested that the microbial biomass acts as an ion exchanger by virtue of reactive groups available on the cell surface. Different chemical groups of the fungal cell wall have been suggested as potential binding sites, such as carboxyl, amine, imidazol, phosphate, sulphydryl, sulphate, hydroxyl groups and the lipid fraction according to the chemical class of the dye (Zhou and Banks, 1993; Aksu and Tezer, 2000; Fu and Viraraghavan, 2002).

Effect of pH on biosorption of RBB by fungal biomass:-
Biosorption of RBB by inactivated biomass of fungal cultures P. chrysosporium, WRF3 and WG1at different initial pH of RBB solution (50 ppm) is shown in the Fig. 3. Acidic pH was reported more suitable for the removal of dye from the dye solution as is evident from the maximum % decolorization in the acidic range. For P. chrysosporium and WRF3 biomass, at pH 4 maximum dye removal was observed (above 80%), while at pH 3 maximum biosorptive removal of RBB was achieved. And in all the three cases, as pH increased, it resulted in decreased biosorption of the dye.
In basic conditions, presence of excess OH ─ competed with the anionic dyes for adsorption sites. For this reason, the biosorption amount of RBB decreased in basic conditions. While, acidic conditions could be favorable for the biosorption between the two dyes and the fungal biomass, because a significantly high electrostatic attraction could exist between the positively charged surface of the biosorbent under acidic conditions and the anionic dyes (Aksu 944 and Donmez, 2003). Maximum biosorption capacities in single system for AB 25 and AR 337 onto unmodified and CDAB-modified biosorbents were obtained at pH 2.0, and then decreased as the pH increased. When the pH of solution changed from 2.0 to 9.0, the biosorption capacities of unmodified biosorbent in single system for AB 25 decreased (Yang et al., 2011b). The biosorption capacity of Penicillium YW 01 increased from pH 1.0 to pH 3.0, and reached maximum at pH 3.0 (46.95 and 48.83 mg g -1 for Acid Black and Congo Red, respectively), and then declined sharply with further increase in pH for both of the two dyes, indicating that the optimal pH for biosorption of Penicillium YW 01 is 3.0 for both of the two dyes under the experimental conditions (Yang et al., 2011a).

Conclusion:-
Three fungal cultures, P. chrysosorium MTCC 787, Aspergillus sp. WRF3 and Trichoderma sp. WG1, were studied for their ability to remove RBB from 50ppm dye solution under shaking conditions. All the three cultures were exhibited high potential for the removal of RBB even at low biosorbent dosage. Acidic pH was more suitable for biosorption of RBB from the solution and 7h contact time was needed for maximal removal of dye (>90%) from the dye solution at 3gL -1 biosorbent dosage. Thus, these cultures can be useful in biosorptive removal of RBB containing wastewaters. However, influence of heavy metals and other pollutants in the industrial effluents needs to be evaluated for successful application of these fungal cultures for biosorptive removal of RBB dye from RBB bearing wastewaters.