Application Of FT-MIR-ATR Online Analysis Technology For The Optimization Of Fermentation Process By Aspergillus Niger

The technology of mid-infrared spectroscopy is a new,rapid,non-invasive and green analysis method.In this study,application of Fourier transform mid-infrared spectroscopy with an attenuated total reflection probe(FT-MIR-ATR)was investigated in the fermentation process by Aspergillus niger.The model was regressed by partial least squares(PLS)method on spectra of standard solutions designed by full factorial design pattern,According to this model,glucose and sodium gluconate concentrations in the broth could be on-line monitored,and subsequently to direct the optimization of gluconate production in the batch and continuous fermentations.Firstly,through improving the standard solution preparation method and the collection condition as well as the pretreatment method,the root mean square error of predictions(g/L)for glucose and sodium gluconate were 3.68 and 4.58,respectively,with their relative errors(%)of 2.16 and 2.08 by the improved model.This results decreased by 21.17%and 49.76%compared with the initial model of 2.74%and 4.14%,respectively.Simultaneously,the on-line prediction presented good relationship with the off-line measurement,and the correlation coefficients were more than 0.99,demonstrating the great potential of FT-MIR-ATR spectroscopy to on-line predict glucose and sodium gluconate accurately in the process control and optimization of A.niger fermentation process.Secondly,above-developed model was adopted to investigate the effects of different initial glucose concentrations as well as different aeration conditions on glucose consumption and product formation in batch fermentation processes.The results showed that the highest productivity of 21.17±0.32 g/(L·h)was obtained with glucose consumption of 20.29±0.37 g/(L·h)when the initial glucose concentration was 300 g/L.Moreover,under the existing experimental conditions,the optimal aeration condition with 10%pure oxygen and 90%air could further enhance the glucose consumption and productivity to 24.29±0.29 g/(L·h)and 23.38±0.35 g/(L·h),Notably,it should be indicated that compared to the previous oxygen uptake rate based method to indirectly calculate glucose consumption rate and product synthesis rate,the values could be directly and accurately obtained from FT-MIR-ATR analysis,which could be further helpful to guide the process strategy development.Lastly,in continuous fermentation process,the feedback system was established on the basis of FT-MIR-ATR analysis technology to control the residual glucose concentrations at 0 g/L,10 g/L and 20 g/L respectively.It was found that 10 g/L residual glucose exhibited the best fermentation performance in stable period with the productivity of 21.56±0.29 g/(L·h),which increased by 7.6%in comparison to 0 g/L residual glucose.The results of GC-MS showed that most metabolites pools of TCA cycle in 10 g/L and 20 g/L residual glucose were higher than those in 0 g/L residual glucose.In conclusion,the introduction of FT-MIR-ATR analysis technology could be acted as a powerful tool to provide technical support for fermentation process optimization of A.niger.