Using fermentation waste of ethanol‐producing yeast for bacterial riboflavin production and recycling of spent bacterial mass for enhancing the growth of oily plants

Aim This study aims to use fermentation waste of ethanol production (solid and liquid) for riboflavin and recycling of bacterial biomass as biofertilizers to enhance the growth of some oily crop plants. Methods and Results Out of 10 yeast isolates from fresh milk, Clavispora lusitaniae ASU 33 (MN583181) was able to ferment different concentrations of glucose (2.5%, 5%, 7.5%, 10%, 15% and 20%) into ethanol with high efficiency at 10%. Among seven non‐Lactobacillus bacterial isolates recovered from cheese samples, two bacterial isolates Bacillus subtlis‐SR2 (MT002768) and Novosphingobium panipatense‐SR3 (MT002778) were selected for their high riboflavin production. Different media (control medium, fermentation waste medium and a mixture of the fermentation waste medium and control medium [1:1]) were used for riboflavin production. These media were inoculated by a single or mixture of B. subtlis‐SR2, N. panipatense‐SR3. The addition of the waste medium of ethanol production to the control medium (1:1) had a stimulatory effect on riboflavin production whether inoculated with either a single strain or a mixture of B. subtlis‐SR2 and N. panipatense‐SR3. A mixture of fermentation waste and control media inoculated with N. panipatense produced a high riboflavin yield in comparison with other media. Inoculation of Zea mays and Ocimum basilicum plants with either the bacterial biomass waste of riboflavin production (B. subtlis or N. panipatense) or a mixture of B. subtlis and N. panipatense) shows a stimulatory effect on the plant growth in comparison with control (uninoculated plants). Conclusions These results demonstrate the possibility of minimizing the cost of riboflavin and biofertilizer manufacturing via interlinking ethanol and riboflavin with the biofertilizer production technology. Significance and Impact of Study This study outlines the methods of evaluating the strength of spent media by applying procedures developed in the vitamin production industries. Furthermore, bacterial biomass waste can act as an environmentally friendly alternative for agrochemicals.