Abstract
Second grade local dates of Bekrari variety were targeted in this study as a substrate for the production of the bakersُ yeast Saccharomyces cerevisiae and its potential use as an alternative for molasses which considered as the conventional substrate for yeast production. The production process consisted of four stages: extraction of the syrup from dates with the method that applied at the date syrup factory in Al-Khoms city, comparing its chemical composition with molasses, determination of the chemical composition suitability of date syrup for yeast growth, fortification of the novel substrate ( date syrup) to be suitable for optimum cultivation of the yeast as to cover its complete nutritional requirements and comparing the use of date syrup with molasses for biomass production and the fermentation strength of the yeast. The results of the physicochemical analysis of date syrup and molasses demonstrated the following average percentages: 18 and 20% moisture, 69 and 54.6% total sugars, 63 and 49% fermentable sugars, 6 and 5.4% non-fermentable sugars, 4.62 and 9.32% ash, 1.1 and 1.8% protein, respectively. The values of Brix of date syrup and molasses were 77.38 and 75, pH 4.39 and 5.04, density 1.37 and 1.41 g/cm3, respectively. The fermentation processes which were carried out for determination of the optimum conditions for yeast cultivation on date syrup showed that 5% sugar, 0.2% urea (as nitrogen source), 100 mg/L. zinc sulfate, 2 mg/L. copper sulfate, 0.5 and 50 mg/L for biotin and thiaminr respectivety, gave the best results for yeast biomss production as well as the fermentation strength at 32-34 ◦C, pH 4.5-5.5 and agitation rate of 250 rpm. The highest counts of the yeast S. cerevisiae were 80 x 109 and 95x109Cell/g, for the molasses and the date syrup, respectively. Contamination monitoring during the fermentation processes indicated that the yeast Saccharomyces cerevisiae was free of the contaminating yeast in both media. However, the total count of contaminatiog bacteria Contaminatiog bacteria ranged between 2 x 104 – 2.2 x 104 of molasses and date syrup respectively. The results of the statistical analysis revealed significant differences (at P= 5%) between date syrup and molasses as substrates for yeast biomass production and its fermentation strength which were 50.2 g/l and 850 cm3 CO2/hr for molasses , 55.2 g/l and 1000 cm3 CO2/hr for date syrup. From these results, it is clear that there is no technological obstacle toward the utilization of date syrup as an alternative substvste for molasses in the production of bakersُ yeast and continuing forward in carrying out studies on the utilization potential of dates which are not suitable for direct human consumption in the production of this strategic and significant commodity inside the Jamahiriya. Key words: Bakersُ yeast ,Date Syrup, Molasses, ُ Yeast Biomass, Fermentation Strength.