The first step of the statistical approach to the analysis
optimization was to establish the criteria that will define
the experimental factors that have a significant effect on
the response variables. Therefore, to optimize the ethanol
production it was first performed as a 24 factorial design.
Four relevant factors for the fermentative process were
selected in a factorial design 24. The variables, studied
simultaneously were: TRS concentration in sugar cane
molasses (150 and 250 g L1), temperature (25 and
35 C), agitation (180 oscillations per minute and static culture)
and culture time (12 and 24 h), as shown in Table 1.
The main effects of the three factors concentration in
sugar cane molasses (2.72), temperature (3.27), and (8.47)
are all positives, and agitation rate is negative (6.66).
The growth time (X4) main effect is the most significant factorial
design effect value for the production of ethanol. The
inclusion of agitation rate reduces the average ethanol production.
Therefore, the subsequent runs were performed in
a static format. Higher ethanol productions, 22.69 g L1
and 30.08 g L1 were obtained in static culture (run 11
and 12 in Table 1). According to Lee and Huang (2000)
Z. mobilis is able to obtain an ethanol production close
to the theoretical one from glucose through Entner–Doudoroff
pathway under aerobic conditions.
The first step of the statistical approach to the analysisoptimization was to establish the criteria that will definethe experimental factors that have a significant effect onthe response variables. Therefore, to optimize the ethanolproduction it was first performed as a 24 factorial design.Four relevant factors for the fermentative process wereselected in a factorial design 24. The variables, studiedsimultaneously were: TRS concentration in sugar canemolasses (150 and 250 g L1), temperature (25 and35 C), agitation (180 oscillations per minute and static culture)and culture time (12 and 24 h), as shown in Table 1.The main effects of the three factors concentration insugar cane molasses (2.72), temperature (3.27), and (8.47)are all positives, and agitation rate is negative (6.66).The growth time (X4) main effect is the most significant factorialdesign effect value for the production of ethanol. Theinclusion of agitation rate reduces the average ethanol production.Therefore, the subsequent runs were performed ina static format. Higher ethanol productions, 22.69 g L1and 30.08 g L1 were obtained in static culture (run 11and 12 in Table 1). According to Lee and Huang (2000)Z. mobilis is able to obtain an ethanol production closeto the theoretical one from glucose through Entner–Doudoroffpathway under aerobic conditions.
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