Background

Synthetic dye wastewater is a group of environmental pollutants that are widely used in some industries like textile, printing, dyeing and etc. Traditional treatment methods for wastewaters containing synthetic dyes are considered as expensive and time consuming approaches due to the chemical stability of these pollutants. Therefore, in recent years, biodegradation by means of capable microorganisms has been considered as an effective way to remove these pollutants. Hence, the present study has aimed at examining the decolorization of Toluidine Red (C.I. no.12120), which is an oil soluble azo dye, as the sole sources of carbon and energy from a synthetic dye wastewater by the halophilic Halomonas strain Gb bacterium. In order to model, optimize, and investigate the individual factors affecting the biodegradation capacity of this dye by Halomonas strain Gb, for the first time response surface methodology (RSM) and central composite design (CCD) were applied.

Methods

In this research, statistical modeling and optimization were performed by Design Expert software version 10 and the degradation capacity was considered by carrying out 30 tests using RSM method. For this purpose, the effect of 4 variables included dye concentration (10–30 ppm), salt concentration (2–10%), pH (5.5–9.5), and temperature (20–40) at different times of 2nd, 4th, and 10th days have been studied. Then, a second-order function was presented for the amount of dye removal in terms of the four selected variables, based on statistical modeling.

Results

According to the obtained results and analysis of variance, all main variables were found to be significantly effective on the biodegradation capacity. With regard to the results, the highest amount of biodegradation between different days was 81% and observed at the 4th day, while the optimum conditions for the maximum biodegradation of this time has been determined at pH of 6.5, temperature of 35 °C, and salt and dye concentrations were equivalent to 4% and 25 ppm, respectively. There is 11% relative error between the experimental and predicted results in the selected experiments, which confirms the reliability of the obtained correlation for calculating the decolorization capacity.

Conclusion

In accordance with the results, the proposed model can provide a good prediction of the effect of different conditions on the biodegradation of Toluidine Red, and the optimization results in this study have been consistent with the previous studies conducted with the IP8 and D₂ strains by the OFAT method. Moreover, the proposed model may help in better understanding the impact of main effects and interaction between variables on the dye removal. Overall, the results indicated that the halophilic bacterium used in dye removal can be more effective in high-salinity environments.

中文翻译：

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使用卤单胞菌菌株 Gb 合成废水中甲苯胺红生物降解的统计建模和优化。

背景

合成染料废水是一组环境污染物，广泛应用于纺织、印染等行业。由于这些污染物的化学稳定性，传统的含合成染料废水的处理方法被认为是昂贵且耗时的方法。因此，近年来，利用有能力的微生物进行生物降解被认为是去除这些污染物的有效途径。因此，本研究旨在检查甲苯胺红（CI no.12120）的脱色，它是一种油溶性偶氮染料，是嗜盐卤单胞菌从合成染料废水中唯一的碳和能源来源菌株 Gb 细菌。为了建模、优化和研究影响该染料被卤单胞菌菌株 Gb 生物降解能力的单个因素，首次应用响应面法 (RSM) 和中心复合设计 (CCD)。

方法

在这项研究中，使用 Design Expert 软件版本 10 进行统计建模和优化，并通过使用 RSM 方法进行 30 次测试来考虑降解能力。为此，4 个变量的影响包括染料浓度 (10–30 ppm)、盐浓度 (2–10%)、pH (5.5–9.5) 和温度 (20–40) 在 2、4 的不同时间，并且已经研究了第10天。然后，基于统计建模，根据四个选定的变量，提出了染料去除量的二阶函数。

结果

根据所得结果和方差分析，发现所有主要变量对生物降解能力均显着有效。就结果而言，不同天之间的最高生物降解量为 81%，在第 4 天观察到，而此时最大生物降解的最佳条件已确定为 pH 6.5、温度 35°C 和盐和染料浓度分别相当于 4% 和 25 ppm。所选实验的实验结果与预测结果之间存在11%的相对误差，这证实了所获得的相关性在计算脱色能力时的可靠性。

结论

根据结果​​，所提出的模型可以很好地预测不同条件对甲苯胺红生物降解的影响，并且本研究中的优化结果与之前对IP8和D ₂菌株进行的研究一致OFAT 方法。此外，所提出的模型可能有助于更好地理解主效应和变量之间的相互作用对染料去除的影响。总体而言，结果表明，用于染料去除的嗜盐细菌在高盐度环境中可能更有效。