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Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011through pre-weighed 13-mm membrane filters (Nalgene, 0.45-µm pore size). The filterswere washed with distilled water twice and then dried at 100°C for at least 16 h to constantweight. The determinations were performed in duplicate and varied by less than 2%.3. RESULTS AND DISCUSSIONSMicroscopy revealed that most of the yeasts produced were pure culture, withhomogeneous cell size and morphology for molasses productions (Fig. 2), with more than98% of live cells as measured by methylene blue stain.Fig. 2 Cell shape of strains for MY2011 yeast produced in the 20-l bioreactor (16 l of culture) withmolasses. The micrographs were taken after the 24-h production run and the scale bar represents 10µm.YEAST YIELD FOR THE FED-BATCH MOLASSES PRODUCTIONThe yield of yeast production with molasses depended on the amount of total sugarexisting during yeast growth. In figures 3 and 4 is given the yield in biomass (YB, in gramsof dry yeast/l) for the tested formulations of culture medium: sugar beet molasses (SBM),sugar cane molasses (SCM) and mixtures (half ratio) of sugar beet and sugar cane molasses(SB+C_M). Also the presence of certain nutrients into the medium growth contributes todifferent biomass accumulation (enrichment for). In this work we used four variousmedium, as it was mentioned above.As is shown in figure 3, the biomass yield increased from a minimum of 24.9 g/lusing blank medium (I) for sugar beet molasses to a maximum value of 33.3 g/l, whenmedium IV and sugar cane molasses were used for.Figures registered throughout our study indicated that the best yield was obtainedusing sugar cane molasses, no matters the media preparation. Obviously, the results wereimproved when they worked with formulation of medium IV in comparison with previousones due to specific enrichments.On the basis of the data introduced in figures 3 and 4, the following remarks canbe drawn on either the influence of type of molasses or ingredients for fermentationpreparation on the biomass accumulation in culture medium:1. For all tests there is an increment in biomass yield with an upward trend of percentage ofthe cane molasses in the culture medium (see also figure 5).128
Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 20112. Increase in yield of biomass in the case of medium II in comparison with medium III issimilar. This is in accordance with literature [Reed and Peppler, 1973; Assessment of VOCemissions, 1992] in that the cane and beet molasses usually provide enough inositol andpantothenic acid for yeast growth.Medium IMedium IIYB, g/l3432302826241 2 3 4 5YB, g/l3432302826241 2 3 4 5SBM SCM SB+C_MSBM SCM SB+C_MMedium IIIMedium IV34343232YB, g/l302826YB, g/l302826241 2 3 4 5241 2 3 4 5SBM SCM SB+C_MSBM SCM SB+C_MFig. 3 Variation of the field in biomass depending on growth medium composition3432YB, g/l30282624Medium I Medium II Medium III Medium IVSBM SCM SB+C_MFig. 4 Mean values for yeast yield production by using different fermentation media3. Differences on biomass growth were register between medium II and medium IV whenvarious molasses used, but bivariate correlation coefficient was not significant at p=0.05.129
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