اکرم زمانی

One of the main applications of chitosan is for heavy metals removal from waste waters. Industrially, chitosan is produced through deacetylation of chitin present in shellfish waste. Another source of chitosan is the cell wall of zygomycetes fungi with several advantages over shellfish wastes. Materials and method s: Fungal chitosan purified from biomass of Mucor indicus and shrimp chitosan were applied and compared for removal of copper ions from aqueous solution. The effects of pH (3 to 5.5), copper ion concentration (5 to 52 mg l-1), the amount of chitosan (200 to 3000 mg l-1), adsorption time, temperature, and presence of other metal ions on the biosorption of Cu2+ were investigated. Maximum adsorption capacities for fungal and shrimp chitosans were 58.5 and 60.7 mg g-1, respectively. T he rate of copper adsorption by the fungal chitosan was significantly higher than that by the shrimp chitosan. Among p seudo-first order, pseudo-second order, intra-particle diffusion, and Elovich models, Ho’s pseudo-second order model was the best model for fitting the kinetic data. The adsorption capacity increased for both types of chitosans by increasing the solution pH. However, temperature and presence of other ions did not show significant effects on the biosorption capacity of copper. The isotherm data were very well described by Langmuir, Freundlich, and Redlich-Peterson models. Discussion and Both fungal and shrimp chitosans can effectively be used for removal of copper ions from aqueous solutions. Adsorption process for fungal chitosan is fast, while the process is slower for the shrimp chitosan. Therefore, from the kinetics point of view, the fungal chitosan is preferable compared with the shrimp chitosan.

In biological production of low value added bioproducts، the substrate cost comprises a significant part of the total price. Therefore، choosing an inexpensive substrate with a high yield of production can greatly reduce the production cost. Starch as an abundant and cheap carbon source can be a suitable substrate for microbial production of xanthan gum. However، in most of the studies on microbial xanthan gum production، glucose has been used as substrate. Materials and method s: In this study، microbial production of xanthan gum using Xanthomonas campestris PTCC 1473 and hydrolyzed starch as carbon source was investigated. The concentration of carbon source and time were optimized using RSM-CCD method. Both factors were regarded to be significant for production of xanthan using hydrolyzed starch.

Based on the obtained results، optimum carbon source concentration and time were 56 g/L and 38. 4 h، respectively. Under optimum conditions، 8. 34 g/L of xanthan gum was produced. Discussion and

The results of this study indicated that starch could be used as a waste and inexpensive carbon source instead of glucose for the production of xanthan gum. It was also shown that the effect of carbon source concentration was more significant than time for xanthan production. In addition، these two factors were independent and did not have any interaction.