Magnetic Nanoparticle-Assisted Immobilized Co-Culture of Saccharomyces cerevisiae and Kluyveromyces marxianus: Effects on Ethanol Production, Sugar Consumption, Biomass Reuse, and Volatile Metabolite Profiles

Yeast-assisted mixed-culture fermentations have gained attention for their ability to enhance fermentation efficiency and modulate metabolite production. There is little knowledge on the impact of magnetic nanoparticle-assisted immobilization on yeast–yeast interactions during alcoholic fermentation. The co-culture platforms of Saccharomyces cerevisiae and Kluyveromyces marxianus, immobilized on chitosan-coated manganese ferrite nanoparticles, were applied in the fermentation of sugarcane molasses and sugarcane juice in the present study. The chitosan-coated MnFe2O4 nanoparticles were prepared using a one-step coprecipitation reaction followed by hydrothermal treatment and were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscopy. An immobilized co-culture system has been shown to provide faster sugar consumption and higher ethanol production than non-immobilized-cell fermentations. Operational stability of the immobilized biomass and higher ethanol production by reuse were confirmed by repeated fermentation cycles. Bioproduction of volatile metabolites varies among monoculture, co-culture, non-immobilized-cell, and immobilized systems, with yeast interactions and magnetic immobilization also affecting secondary metabolite production during fermentation. The findings confirm that magnetic nanoparticle-assisted co-culture fermentation would be an attractive nanobiotechnological tool for enhancing alcoholic fermentation and shed new light on yeast interactions with the nanostructured system when combined with the immobilized solution.