Abstract
The well function of aquatic and soil organisms including terrestrial, as well as those of all other living things, can be jeopardized if dyes aren't properly treated, as their degradation might lead to carcinogenic chemicals. Complete mineralization of dye is the only option, and this can be done using microorganisms. The azo blue dye inhibitory effect to its biodegradation by Streptomyces DJP15 was modelled using several inhibition kinetic models such as Haldane, Monod, Luong, Aiba, Teissier-Edwards, Han-Levenspiel and Yano. The result shows that only the Luong model failed to fit the data. The rest of the models visually ft the data although data fitting is problematic with datapoints of less than 10, which the result in this work demonstrates where it is not easy to choose the best model where nearly all of the models fit the data in a similar manner. Resorting to statistical discriminatory function, the best model was Monod with the smallest RMSE and AICc values and the highest adjR2 values and values for AF and BF close to unity. However, Monod has only two parameters and is the most robust. The Monod’s parameters were maximum specific degradation rate of 0.431 (1/h) (95% confidence interval from 0.391 to 0.456) and concentration of substrate giving half maximal rate or Ks value of 0.0001 (mg/L) (95% C.I. from -0.01 to 12.12). The confidence interval value for the Ks value was very large indicating poor data quality. This should be an important consideration in future works where the data point number can be increased to improve model fitting exercise.
Highlights
Azo dyes are the most common and versatile synthetic dyes used in the textile industry, accounting for more than half of all synthetic dyes manufactured each year [1]
A previously published data [3], from Figures 2 which shows the degradation of Azo blue by streptomyces DJP15 at different concentrations were used in this study
Statistical analysis An experiment was used to compare the quality of models with various numbers of parameters, and data were analysed using numerous statistical approaches including adjusted coefficient of determination, the Root Mean Square Error (RMSE), bias factor (BF), accuracy factor (AF), and AICc, which is a corrected form of the original Akaike Information Criterion (AIC) to see if a statistically significant difference existed (Akaike Information Criterion) [23]
Summary
Azo dyes are the most common and versatile synthetic dyes used in the textile industry, accounting for more than half of all synthetic dyes manufactured each year [1]. They're the only azo dyes that can bind covalently to cellulosic fibre and are widely used in the textile industry." They are very water-soluble and non-degradable in the normal aerobic conditions seen in biological treatment systems because of their strong sulphonation [4]. There are several -SO3H- group dyes in industrial effluents that are sulfonated azo dyes. Antidegradation properties are seen in the vast majority of azo dyes. The dyes are poisonous and inert due to the presence of sulfo and azo groups, which aren't found in nature [5]
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