3.2. Microorganism maintenance during storage
Synthesis of the bio-films must be optimized both to prolong microorganism viability and distribution and to improve the inhibitory efficiency of the films on mold growth during storage. The influence of nutrient concentration on microorganism viability during storage also needed to be evaluated.
Effects of carbon source at different concentrations on the population of C. laurentiientrapped in SA are shown in Fig. 1. Compared to the values at the beginning of the experiment, yeast viability at the end of 20 d storage remained at about 49.7%, 81.9% and 76.6% for the control, 3% CS and 6% CS, respectively. It is shown that the concentration of viable yeast cells in the alginate film without the carbon source changed rapidly during storage. For the group with 3% CS, the concentration of viable cells steadily decreased with storage time. However, for the 6% CS, the concentration of viable cells did not change appreciably over 20 d.
The profiles in Fig. 1 show that the optimal nutrient concentration was equal to or higher than 6%. The local nutrient concentration did not present a limiting factor to viability during storage of the entrapped cells, suggesting that the optimal value for the initial nutrient concentration was 6%.