Abstract
The interaction between nanostructures and yeast cells, as well as the description of the effect of nanoparticles in ethanol production are open questions in the development of this nanobiotechnological process. The objective of the present study was to evaluate the ethanol production by Saccharomyces cerevisiae in the free and immobilized state on chitosan-coated manganese ferrite, using cane molasses as a carbon source. To obtain the chitosan-coated manganese ferrite, the one-step coprecipitation method was used. The nanoparticles were characterized by X-ray diffraction obtaining the typical diffraction pattern. The crystal size was calculated by the Scherrer equation as 15.2 nm. The kinetics of sugar consumption and ethanol production were evaluated by HPLC. With the immobilized system, it was possible to obtain an ethanol concentration of 56.15 g/L, as well as the total sugar consumption at 24 h of fermentation. Productivity and yield in this case were 2.3 ± 0.2 g/(L * h) and 0.28 ± 0.03, respectively. However, at the same time in the fermentation with free yeast, 39.1 g/L were obtained. The total consumption of fermentable sugar was observed only after 42 h, reaching an ethanol titer of 50.7 ± 3.1, productivity and yield of 1.4 ± 0.3 g/(L * h) and 0.25 ± 0.4, respectively. Therefore, a reduction in fermentation time, higher ethanol titer and productivity were demonstrated in the presence of nanoparticles. The application of manganese ferrite nanoparticles shows a beneficial effect on ethanol production. Research focused on the task of defining the mechanism of their action and evaluation of the reuse of biomass immobilized on manganese ferrite in the ethanol production process should be carried out in the future.
Highlights
The possibility of obtaining a renewable source of energy that is easy to access, safe and effective is one of the goals that humanity must achieve
Applying the one-step coprecipitation procedure proposed by Osuna et al (2012) with modification by hydrothermal treatment in an autoclave, the dark brown materials susceptible to the effect of external magnetic field were obtained, which were characterized by different methods to verify that it is magnetic manganese ferrite nanoparticles with and without chitosan
Goodarz et al (2011) synthesized manganese ferrite nanoparticles using a heat treatment method followed by calcination
Summary
The possibility of obtaining a renewable source of energy that is easy to access, safe and effective is one of the goals that humanity must achieve. Ethanol obtained by biotechnological methods is an important alternative to fossil fuels. The most common microorganisms used in fermentation from are the yeasts, especially, S. cerevisiae, though the bacterial species Zymomonas mobilis is potentially used nowadays for this purpose (Arshad et al, 2018). In an attempt to improve ethanol fermentation, cell immobilization techniques have been developed to increase the rate of ethanol production, keep cells in a viable state, and achieve their normal function (Zapata and Peláez, 2010). In the immobilization of fungal spores and yeast cells, magnetic nanoparticles were used (Palacios et al, 2017). Nanoparticles have the ability to bind to the cell surface helping in the biomass separation and the biocatalysts reuse, since under the application of an external magnetic field, the particles are attracted and precipitated keeping the immobilized cells (Palacios et al, 2017)
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