Definition of optimum basic nutrients ratio in media for bioethanol production with immobilised yeast cells

The production of bioethanol as an alternative to fossil fuel has been increasing owing to growing biofuel demand. Combination of yeast immobilisation and media optimisation has become a popular technique for the improvement of bioethanol technology. The aim of this study was the optimisation, by response surface methodology, of sodium alginate concentration and nitrogen and phosphorus content in media for bioethanol production using immobilised Saccharomyces cerevisiae. Ratio of carbon, nitrogen and phosphorus (C : N : P) in media was calculated based on optimum factors values and initial glucose content. The developed model predicts that maximum product concentration, minimum 'eluted' yeast cells number and minimum nutrients content are achieved when the sodium alginate concentration is 71.99 g/L and C : N : P ratio is 50 : 3.5 : 1.3. The obtained results can be used for techno-economic analysis of the process to select optimum fermentation conditions for industrial application.