The results observed for the Total Residual Reducing Sugar (TRRS) content of the broth after fermention process are at the Table 01 indicate it was no significant difference between the genotypes when the yeast CAT-1 was used in the fermentation process.
Table 1
Results of the analysis of variance (F test) and Tukey test comparison of means (5% probability) for the chemical-technological characteristics of the broth after fermentation process. Jaboticabal-SP.
|
TRRS
(%)
|
Total Acidity
(g.L-1 H2SO4.L-1)
|
pH
|
Glycerol
(mg.100mL-1)
|
Genotypes (A)
|
CAT-1
|
PE-2
|
CAT-1
|
PE-2
|
CAT-1
|
PE-2
|
CAT-1
|
PE-2
|
CVSW80007
|
1.99A
|
2.60A
|
3.52A
|
3.57A
|
3.67C
|
3.80C
|
9.01A
|
8.78A
|
CVWS80147
|
1.62A
|
1.82AB
|
3.89A
|
3.74A
|
3.79B
|
3.94B
|
8.60A
|
7.72B
|
BRS610
|
0.79A
|
0.73B
|
3.61A
|
3.49A
|
3.94A
|
4.07A
|
6.90B
|
5.92C
|
F Test
|
6.14ns
|
15.37*
|
5.77ns
|
1.33ns
|
40.79**
|
53.48**
|
13.27*
|
95.86**
|
MSD
|
1.25
|
1.20
|
0.40
|
0.55
|
0.10
|
0.09
|
1.54
|
0.74
|
CV
|
101.17
|
83.19
|
13.22
|
18.39
|
3.28
|
2.77
|
22.48
|
11.82
|
Leaves (B)
|
|
|
|
|
|
|
|
|
With leaves
|
1.20A
|
1.50B
|
3.68A
|
3.60A
|
3.85A
|
3.97A
|
7.77B
|
7.15A
|
Without leaves
|
1.73A
|
1.94A
|
3.67A
|
3.61A
|
3.75B
|
3.90B
|
8.58A
|
7.79A
|
F Test
|
5.12ns
|
6.87*
|
0.03ns
|
0.01ns
|
18.74**
|
10.11*
|
9.05*
|
2.69ns
|
MSD
|
0.57
|
0.40
|
0.17
|
0.36
|
0.05
|
0.05
|
0.65
|
0.95
|
CV
|
83.12
|
50.29
|
10.28
|
21.31
|
3.01
|
2.97
|
17.09
|
27.21
|
Harvesting time (C)
|
|
|
|
|
|
|
|
|
100
|
1.23AB
|
1.54A
|
4.03A
|
4.48A
|
3.86AB
|
3.89B
|
7.15B
|
7.16A
|
105
|
1.78A
|
1.44A
|
3.94AB
|
3.47BCD
|
3.65C
|
4.05A
|
9.72A
|
7.12A
|
110
|
1.92A
|
2.15A
|
3.93ABC
|
3.85B
|
3.62C
|
3.69C
|
8.09AB
|
8.04A
|
118
|
1.44AB
|
1.87A
|
3.47CD
|
3.02D
|
3.79B
|
4.01AB
|
8.27AB
|
7.19A
|
135
|
1.72A
|
1.90A
|
3.17D
|
3.12CD
|
3.92A
|
4.06A
|
7.55B
|
7.21A
|
160
|
0.70B
|
1.40A
|
3.49BCD
|
3.67BC
|
3.96A
|
3.92AB
|
8.25AB
|
8.13A
|
F Test
|
3.49**
|
1.87ns
|
9.37**
|
13.77**
|
22.86**
|
12.62**
|
4.95**
|
2.39*
|
MSD
|
1.00
|
0.91
|
0.46
|
0.59
|
0.12
|
0.16
|
1.64
|
1.27
|
CV
|
69.41
|
53.98
|
12.94
|
16.85
|
3.28
|
4.17
|
20.50
|
17.39
|
Inter. AxB
|
0.26ns
|
1.34ns
|
0.02ns
|
2.12ns
|
1.86ns
|
1.02ns
|
1.16ns
|
1.38ns
|
Inter. AxC
|
1.58ns
|
1.31ns
|
1.44ns
|
1.01ns
|
1.31ns
|
1.35ns
|
1.31ns
|
2.36*
|
Inter. BxC
|
0.62ns
|
0.69ns
|
0.79ns
|
0.54ns
|
0.33ns
|
0.25ns
|
0.60ns
|
0.62ns
|
Inter. AxBxC
|
0.85ns
|
0.91ns
|
2.72**
|
2.93**
|
0.16ns
|
1.03ns
|
1.14ns
|
0.91ns
|
The averages followed by the same letter do not differ statistically from each other (Tukey test 5%). The letters compare averages in the column. ** significant at the 1% probability level (p<0.1) * significant at the 5% probability level (0.1 = <p <0.5). MSD – Minimum Significant Difference. CV - Coefficient of Variation.
|
When used PE-2 yeast as inoculum these differences were significant. Considering the genotypes, it was verified that BRS610 presented a significantly lower value than CVSW80007, which presented higher mean values. The presence of leaves resulted in a significantly lower value of total residual reducing sugar for PE-2, whereas for CAT-1. Although it hass no significant effect, the highest average was for stalks without leaves. About the harvesting time, it has no significant effect for PE-2, and at 160 days after sowing a significant effect was observed for CAT-1, presenting lower averages. These values can be considered high when compared to those obtained for broth fermented from sugarcane.
Considering the total acidity of the broth after fermentation process, it was verified that there was no significant effect for the genotypes and the processs with or without leaves, independently of the yeast used (Table 01). There was a significant result, at the 1% level, only for the interaction AxBxC, that is, different behavior for the different genotypes, submitted to the harvest systems in the studied harvest time.
The pH of the fermented broth showed the same behavior for both yeasts (Table 01), for both genotypes and systems process. BRS610 presented a significantly higher mean than CVWS80147 and CVSW80007, which had the lowest pH. Considering the presence of leaves and panicles, it was verified a higher pH value in the broth after fermentation process, and for the last sampling seasons these were higher for the two yeasts.
In this study, it has evaluations carried out for the fermented broth at 135 days after sowing, which was considered one of the indicated seasons for the processing of the stalks for ethanol production. From the results obtained, the fermentation efficiency are presented in Figs. 01, 02, and 03.
The results indicated that the process without leaves was more adequate for all the genotypes studied, considering the fermentation efficiency. It can be verified that for the genotype CVSW80007, when the stalks was processed with and without leaves, using yeast CAT-1 showed higher efficiency than PE-2 (Fig. 01), of the order of 6 to 8%.
However, CVWS80147 (Fig. 02) for without leaves and the yeast PE-2 provided the best efficiency, but similar to CAT-1. However, stalks with leaves in CVWS80147 showed no difference for both yeasts.
BRS610 genotype is considered forage, with differents characteristics, mainly the high potential of biomass production. However, when planning the trial was defined as including this treatment and comparing it to the other sweet sorghum genotypes, it was observed that and stalks processed with and without leaves resulted in higher efficiency when PE-2 yeast was used as inoculum in the fermentation process (Fig. 03). When the yeast was CAT-1, results were lower than those found for PE-2 and did not differ from each other.
In order to compare the performance of the studied genotypes using CAT-1 and PE-2 yeast as inoculum of the fermentation process, the yields for theoretical and produced alcohol and were calculated in L.ha− 1 and L.t− 1, are in Figs. 4 and 5. Using sorghum stalks without the presence of leaves and panicles, the average production of 1059 L.ha− 1 of theoretical ethanol, varying from 980 to 1062 L.ha− 1, it was observed for the genotypes CVWS80147 and BRS610, respectively (Fig. 04).
When processing included leaves and panicles a variation of 1522 to 1905 L.ha− 1 of theoretical ethanol was observed, respectively for CVSW80007 and CVWS80147. That can be verified that the processing of leaves and stalks with resulted in an increase of 58% in the ethanol production (L.ha− 1) compared to the process without leaves. These results demonstrate the harvesting time of sorghum stalks, without leaves, does not impact the raw material for the preparation of the broth and fermentation process. From the analysis of the results obtained for the Alcohol Produced (L.ha− 1), it was verified that the processing of leaves less stalks resulted in an average production of 996 L.ha− 1, where the presence of leaves and panicles was of the order of 1530 L.ha− 1. Considering the two yeasts used in the fermentation process, they presented similar behaviors. During the fermentation process carried out using with leaves stalks, genotype CVWS80147 presented the highest yields (Fig. 04).
Calculation of the expected yield of ethanol per processed ton (Fig. 05) ranges from 40 to 49 L.t− 1 when processed stalks with leaves and 47 to 52 L.t− 1 when processed stalks without leaves. The general, the yield for the processed with leaves was 10.75% less. For the genotype CVWS80147, with the average yield of ethanol (Fig. 05), it can be used without leaves it an average yield of 47.0 L.t− 1, whereas for with leaves was 39.8 L.t− 1, that results in a reduction of about 15%. The yeasts used showed similar behavior for genotype CVWS80147. However, for genotypes CVSW80007 and BRS610, it was found that CAT-1 and PE-2 showed better behavior, respectively. Although processing stalks with leaves results in lower ethanol yields (Fig. 05), it should be considered that the higher yield (L.ha− 1) it was a consequence of the total biomass is 77.7% higher than that quantified for the treatment without leaves and panicles.