Impact Of N And P On The Time-course Of SPSC01 De-flocculating And Ethanol Fermentation Performances

The focused laser-beam reflectance measurement (FBRM) was used in the on-line monitoring of yeast floe size distribution under continuous ethanol fermentation. The time-course of the flocculating/de-flocculating of an industrial self-flocculating yeast strain SPSC01, a fusant from Saccharomyces cerevisiae and Schizosaccharomyces pombe, was quantitatively investigated for three industrial media supplemented with 0, 0.15, 3 gl^-1 phosphate, respectively. The deflocculating of yeast flocs was observed as ethanol fermentation going through 20-50 days. An exponential function model was correlated to simulate this time-course deflocculating.(without extra phosphate supplementation)The half-life of yeast floc deflocculating was predicted to be 82, 44, 46 days. Effective factors, ηs and ηp, were further calculated, and it was found that both ηs and ηp were close to 1.0, which indicates the deflocculating of SPSC01 does not exert significant influence on glucose uptake and ethanol formation.Furthermore, the effect of deflocculating of SPSC01 on yeast cell immobilization was evaluated by comparing the biomass concentration suspended in the effluent overflowed from fermentor with that within fermentor. The experimental results illustrated more than 80% yeast cells were retained and immobilized within fermentor although the mean of yeast flocs decreased to about 80 μm from initially about 130 μm. Taking into account all above effects and economic benefit, the concentration of phosphorus in the medium is recommended to be about 0.25 g l^-1in total, and 0.15 g l^-1 phosphate needs to be supplemented for two-stage enzymatic hydrolysate of corn powder used for ethanol production in industry.Finally, the influence of inorganic nitrogen in defined media on flocculating and growth of SPSCOl was studied by flask batch fermentations. The experimental data showed that 0.28 g 1"' nitrogen supplementation could satisfy the basic requirement for both growth and flocculating of SPSCOl, which provides a guideline for formulating industrial medium.