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The potato (Solanum tuberosum L.) is the fourth crop of food in the world, with 377 millions of ton after the corn, rice and wheat (FAO 2015).This cultivation generates many wastes of tubers, not suitable for human consumption, which polluted the environment. These wastes could be converted, with simple technology, into a good quality food for cattle, to low cost (Elías et al. 2008 and Borras 2017).
In Colombia, the post-harvested wastes of potato are use as an alternative in animal feeding. They are added to the diet fresh, to low levels, that is a great amount is throw away, conduct that caused environmental and health problems, due to the pest propagation in crops. However, the application of the solid-state fermentation (SSF) technology of these wastes, as a use alternative in animal nutrition, could fulfill two functions: improve the nutritional quality (Zhou et al. 2019) of the used foods and, specially reduce the environmental pollution that generates the final use of these wastes. In addition, the deep knowledge of the metabolism and the physiology of the acid lactic bacteria (ALB) in microbial preparations, as inoculants (Muck et al. 2018) previous to the fermentation of different fermentation substrates, allowed generate microbial mixtures more defined and reproducible in the quality of the final product (Bintsis 2018)and probiotic activity (FAO 2016).
Borras (2017), in a study performed in the fermentation of potato wastes with a microbial preparation with lactic activity, suggested that these fermentations should be corrected with the inclusion of fibrous plant material that acted as drying and have more consistency, due to the high humidity they have, even after adding calcium carbonate (CaCO3) as drying additive. In this way, they improve the organolectic conditions, possible losses of nutrients by excessive lixiviation in the post-harvested wastes during the fermentation are avoided and it achieves their preservation in the time (Bartova et al. 2015).
The objective of this study was to evaluate the effect of the fibrous materials inclusion on the solid-state fermentation of post-harvested wastes of S. tuberosum, inoculated with a microbial preparation with lactic acid activity.
Materials and Methods
The experiment of solid-state fermentation (SSF) was carry out under the high tropic conditions (2860 m o.s.l.), in the laboratory of biochemical and animal nutrition from Universidad Pedagógica y Tecnológica de Colombia (UPTC), located in the north central avenue, Tunja-Paipa road, in Tunja municipality, Boyacá department, Colombia. This region has an average temperature of 15°C and annual average rainfalls of 553 mm.
Experimental procedure. A yogurt with the active strains Lactobacillus delbrueckiis ssp. bulgaricus and Streptococcus thermophilus (commercial freeze-dried, Liofast Y452B, SACCO ®) was prepared, which was used as inoculum (2 %, v/v and concentration of 0.99 x 108 UFC/mL) to obtain the microbial preparation, according to Borras (2017) methodology. The preparation was mixed with the draying plant material, calcium carbonate at 15 and 25 %. The composition of them is described in table 1.
Table 1 Composition of the fibrous plant material used in the solid-state fermentation of post harvested wastes of S. tuberosum
| Indicators (%) | Fibrous plant material | ||
|---|---|---|---|
| Wheat bran | Alfalfa meal | Rice meal | |
| DM | 87.7 | 87.5 | 91.7 |
| As | 5.0 | 10.4 | 8.3 |
| CP | 15.1 | 16.0 | 13.0 |
| CF | 9.8 | 34.6 | 7.5 |
| EE | 3.5 | 1.98 | 17.2 |
Source: Laboratory of Nutrition and Animal Feeding (UPTC 2013)
The ingredients were mixture until obtaining a homogeneous paste. They were distributed in plastic bags, with 1 kg capacity. Later, the bags were incubated at 20 °C temperature in individual Memmert® incubators, for 48h. Each bag represented an experimental unit, with three repetitions each, according to each treatment. Samples were taken at 0, 24 and 48h of fermentation.
The content of the bags of each treatment was collected in its entirety and was homogenized. Then, 5g of sample were taken and placed in 100 mL Erlenmeyers and 45 mL of sterile distilled water was added, with three repetitions. The preparation was shaken for 30 minutes on an Adams® electric shaker. Later, the filtrate was obtained for pH measurement on an Okaton® automatic potentiometer, in order to carry out the microbiological analysis.
The total of solids left in the bags were dried and ground in a UDY®, hammer mill with a 1 mm sieve, for chemical quantification analysis. For the analysis of dry matter (DM) and crude protein (CP), it was proceeded according to the AOAC (2005).For true protein (TP) Berstein was fallowed , cited by Meir (1986), and for the neutral detergent fiber (NDF) and acid detergent fiber (ADF), van Soest et al. (1991).
The ammoniac (NH3) was determined by Berthelot technique (Martínez et al. 2003).The quantification of short change acids (SCFA) was performed by the method suggested by Dinkci et al. (2007). By means of high efficiency liquid chromatography HPLC the Gemini 5u C18 110A (PHENOMENEX) column was used, with UV light detector vis at 214 nm, at room temperature (15 °C), with mobile phase of (NH4)2 PO4 0.5 % W/V; Acetonitrile 0.4 % V/V. The pH was fitted at 2.24 with H3PO4 (filtered with 0.22 μm pore membrane and degassed by sonication and bubbling with hydrogen) and a flow rate of 0.5 mL/min was applied. It was quantified with the Claritychrom program, version 5.0.5.98.
The microbiological composition was determined to the samples of 0, 24 and 48h of fermentation, in a certified laboratory for the microbiological control, located in Boyacá, Colombia. For aerobic mesophiles (forming colony units per milliliter, UFC/mL) (AOAC 966.23.C: 2001), total and fecal coliforms, most probably number (MPN) (ICMSF NMP: 2000), spores of Clostridium sulfite reductor (UFC/mL), (ISO 15213: 2003), fungi and yeasts (UFC/mL) (ISO 7954: 1987), Salmonella (AS 5013.10: 2009), lactic acid bacteria (LAB) (NTC 5034: 2002).
Analysis of variance was carried out according to a completely randomized design, with factorial arrangement (3x3), for the indicators CP, TP, DM ,NDF, ADF, pH, organic acids, lactic acid and NH3.The factors, for 15 and 25 % of inclusion, were the fibrous plant material( wheat bran, alfalfa meal and rice meal) and the fermentation time (0, 24 and 48 h).
The Duncan (1955) test for P <0.05 was applied in the necessary cases. The statistical package used for the analysis was INFOSTAT, version 2012 (Di Rienzo et al. 2012). For the microbial counting, the data did not fallow the normal distribution, which is why they were transformed according to logX.
Results and Discussion
The indicators in study for the dynamic of SSF of post-harvested wastes of S. tuberosum, inoculated with the microbial preparation, showed interaction between the evaluated fibrous materials and the fermentation time (tables 2, 3 and 4).
With the three evaluated plant materials, the fermentation pH decreased. At 48h, and with the inclusion of wheat bran, the lower value was obtained (4.73). In this case, the indicator was not stabilized, even when 0.50 % of LAB populations were added (Borras 2017). The inclusion of 15% of alfalfa meal and rice meal favors, this indicator, maintaining values in the ranges for the microbial growth (P < 0.0001).These results could be due to, probably, to the chemical composition of the fiber of each material.
The ammonia concentration slightly increase in the fermentation with the inclusion of the three fibrous materials, and the highest value was obtained for the alfalfa meal (7.07 meq/L). According to Aranda et al. (2012), during the SSF process, the microorganisms requires nitrogen sources as the urea, and soluble carbohydrates as molasses, for turn by means of metabolic reactions the non protein nitrogen into protein nitrogen, maximizing the efficient use of NH3 in the amino acids synthesis. In addition, when the pH is low, the NH3 produced during the fermentation is retained in the substrate, it is concentrated and their use is limited by some microorganisms that are in the product for the formation of their cell protoplasm. Zhang y Wang (2013) showed that in the fermentation of food wastes, the CaCO3 maintains the necessary stability to obtain good yield and microbial growth. Therefore, the adding of this additive in 0.50 % achieved to maintain the stability in the organic acid production.
The results of the organic acids study showed absent of the acetic acid, butyric acid, isovaleric acid, isobutyric acid, and slightly production of lactic acid with corn meal, which can indicate that the addition of 15% of fiber of the different plant materials affects the fermentative yield of the LAB, with the decrease of the lactic acid, even when CaCO3 was added in 0.50 % for the pH stability. However, at 48h, with the addition of rice meal was higher (8.23 mmol/L). According to Pejin et al. (2015), the calcium carbonate have significant effect on the lactic acid production by L. lactis as neutralizing agent, providing a favorable microenvironment to the cell. In addition, Martínez et al. (2003) reported that the minerals particles as calcium can benefits the growth and the microorganisms activity, and to absorb part of the organic matter. This could be use by the bacteria to synthesize and turn into energy, activating many enzymatic reactions or maintaining the normal physiological state of microorganisms, which was not observed for these indicators, probably by a dilution or disintegrative effect with the added fiber.
Table 2 Effect of the inclusion of 15% of fibrous plant material on the pH, NH3 and lactic acid of solid fermentation of post-harvested wastes of Solanum tuberosum, inoculated with a microbial preparation
| Indicators | Time, h | Fibrous plant material (15 %) | SE ± Sign | ||
|---|---|---|---|---|---|
| Wheat bran | Alfalfa meal | Rice meal | |||
| pH | 0 | 6.77 h | 6.18 g | 6.78 h | 0.014 P<0.0001 |
| 24 | 5.38 d | 5.72 e | 5.82 f | ||
| 48 | 4.73 a | 5.17 c | 5.04 b | ||
| NH3 (meq/L) | 0 | 2.15 a | 3.46 c | 2.90 b | 0.004 P<0.0001 |
| 24 | 4.55 e | 6.63 g | 4.53 d | ||
| 48 | 6.79 h | 7.07 i | 5.87 f | ||
| Lactic acid (mmol/L) | 0 | 0.002a | 0.002a | 0.002 a | 0.003 P<0.0001 |
| 24 | 0.002a | 0.002a | 1.02 c | ||
| 48 | 0.002a | 0.67b | 8.23 d | ||
a, b, c, d, e, f, g, h,i Means with different letters show differences to P < 0.05, according to Duncan (1955)
Table 3 shows the effect of the inclusion of 15% of the fibrous plant material on the protein content and fiber content during the solid fermentation of post-harvested wastes of S. tuberosum, inoculated with the microbial preparation. The results showed interaction between the evaluated indicators and the fermentation time (P < 0.0001).
Table 3 Effect of the inclusion of 15% of the fibrous plant material in the chemical composition during the solid fermentation of post-harvested wastes of S. tuberosum, inoculated with the microbial preparation.
| Indicators, % | Time, h | Fibrous plant material (15 %) | SE ± Sign | ||
|---|---|---|---|---|---|
| Wheat bran | Alfalfa meal | Rice meal | |||
| CP | 0 | 23.65 c | 19.75 a | 23.73 c | 0.416 P<0.0001 |
| 24 | 31.74 e | 19.01 a | 21.05 b | ||
| 48 | 29.36 d | 21.90 b | 24.38 c | ||
| TP | 0 | 17.44 e | 13.55 c | 16.43 d | 0.158 P<0.0001 |
| 24 | 17.61 e | 11.63 a | 11.60 a | ||
| 48 | 16.57 d | 12.93 b | 13.89 c | ||
| DM | 0 | 73.40 g | 77.86 i | 76.78 h | 0.011 P<0.0001 |
| 24 | 66.67 d | 68.47 f | 61.98 a | ||
| 48 | 63.13 b | 65.63 c | 67.07 e | ||
| NDF | 0 | 48.61 c | 53.93 e | 63.34 i | ±0.013 P<0.0001 |
| 24 | 46.94 b | 49.44 d | 62.66 h | ||
| 48 | 61.11 g | 35.76 a | 57.32 f | ||
| ADF | 0 | 18.96 g | 26.26 i | 5.74 b | ±0.015P<0.0001 |
| 24 | 23.02 h | 15.24 f | 4.84 a | ||
| 48 | 14.98 e | 11.96 d | 6.95 c | ||
| Cell content | 0 | 51.39c | 46.07b | 36.66a | 0.010 P<0.0001 |
| 24 | 53.06c | 50.56b | 37.34a | ||
| 48 | 38.89a | 64.24c | 42.68b | ||
| Hemicellulose | 0 | 29.65b | 27.67a | 57.60c | 0.020 P<0.0001 |
| 24 | 23.92a | 34.20b | 57.82c | ||
| 48 | 46.13b | 23.80a | 50.37c | ||
a, b, c, d, e, f, g, h, iMeans with different letters showed differences to P < 0.05, according to Duncan (1955)
In the composition of raw matter used as fibrous plant material, the CP of the wheat bran, alfalfa meal and rice meal was 15, 16 and 13 %, respectively. A notable increase occurs when they are mixture with the microbial preparation as biological accelerator with respect to the fermentation time (P < 0.0001), according to that published by Borras (2015). In addition, there was a marked effect on the wheat bran at 24h, with difference of 16.74 percentage units with respect to the protein of the origin material. For the alfalfa meal and rice meal, these differences were 8.57 and 12.79 percentage units. However, the relation (TP/CP x 100) shows that for this percent of inclusion this indicator is high in the alfalfa meal (61.55 %). It is fallow by the wheat bran (55.48 %), and then the rice meal (53.48 %) at 24 h. These results showed that the fermentation indicators (pH and organic acids) favor this relation with increase of the biomass in all cases with respect to the control (8.84 %) of the fermentation with the microbial preparation according Borras (2017) to previous studies.
Ramos (2006), when using different substrates by SSF with low protein content, as rice meal, corn, sorghum and dehydrated citric pulp and energetic sources, increased the CP values, from 17.5 to 22.9 %, and the TP from 10.6 to 13.3 %.This author stated that this type of food could compete with commercial, when increasing their nutritive value.
Respect to the dry matter, the inclusion of 15% of plant material favored this indicator in all cases, with significant interaction during the fermentation time (P < 0.0001), and when showed the drying action of the evaluated materials. At 48h of fermentation, there was decrease of the indicator for the wheat bran and the alfalfa meal, of 10.27 and 12.23percentage units, with respect to 0h, respectively; while with the rice meal there was a concentration effect. The decrease of the DM it could due to the hydrolysis of the urea contained in the microbial preparation mixture and, possible, in low scale, to the desamination of peptides and amino acids with ammonia production. However, these values were lower. According to Rodríguez (2004), the ammonia could volatilize, depending on the final pH of the process, by the microorganisms in the ecosystem during the metabolic process for the cell synthesis, oxidizing to fatty acids, CO2 and H2O.
In the fermented alfalfa meal, the NDF decreased in 18.17 percentage units, while in the rice meal the decrease was 6.02 %.However, in the wheat bran this indicator was concentrated in 12.5 percentage units, probably due to the own material composition. It is possible that the decrease in the fiber, when adding the fibrous material is related with a disintegration effect (Ramos et al. 2007), and the microorganisms used in the microbial preparation, produced concentrations of lactic acid and other acids that acts in the fiber. A similar effect was found for the ADF, where there was decrease with the inclusion of wheat bran (3.98 %) and alfalfa meal (14.3 %), not in the same way for the rice meal. For the indicators cell content and hemicelluloses, there were variations according to the fibrous material and the time, without a precise performance.
Table 4 shows the effect of the inclusion of 15% of the fibrous plant material on the microbial concentrations during the solid fermentation of post-harvested wastes of S. tuberosum, inoculated with the microbial preparation. In the samples analysis there was not potential pathogens (Salmonella and Clostridium), or coliforms, and there was growth of yeats and lactic bacteria. These lats show a very important growth at 48h, one hundred times more in alfalfa meal and wheat bran, in contrast to rice meal. This showed the effectiveness of the used inoculum, and the plant material used limited a little their growth. This result coincides with those found in the evaluated chemical indicators.
Table 4 Microbiological analysis of the fermentation of post-harvested wastes of S. tuberosum with microbial preparation and inclusion of 15 % of fibrous material
| Indicator log UFC/mL (UFC/mL) | Incubation time | Fibrous plant material (15 %) | SE± sign | ||
|---|---|---|---|---|---|
| Wheat bran | Alfalfa meal | Rice meal | |||
| Aerobic mesophilic | 0 | 5.12c (1.3x105) | 5.07b (1.2x105) | 5.22d (1.7x105) | 0.02 P<0.0001 |
| 24 | 7.99g (9.7x107) | 7.65f (4.4x107) | 5.01 a (1.0x105) | ||
| 48 | 8.06h (1.0x108) | 7.67f (4.7x107) | 6.97e (9.3x106) | ||
| Yeasts | 0 | 4.44e (2.7x104) | 4.04cd (1.1x104) | 3.98c (1.0x103) | 0.02 P<0.0001 |
| 24 | 3.78b (6.0x103) | 4.06d (1.2x104) | 3.78b (6.0x103) | ||
| 48 | 3.48a (3.0x103) | 5.56f (3.6x105) | 5.81g (6.5x105) | ||
| Lactic acid bacteria | 0 | 5.70c (5.0x105) | 5.04a (1.0x105) | 5.31b (2.0x105) | 0.01 P<0.0001 |
| 24 | 7.41f (2.6x107) | 7.05e (1.1x107) | 5.30b (2.0x105) | ||
| 48 | 7.99h (9.9x107) | 7.48f (3.0x107) | 6.59d (3.9x106) | ||
a, b, c, d, k Means with different letters show differences to P < 0.05, according to Duncan (1955)
Data were transformed according to log10 (X) because they do not follow a normal distribution ( ) Mean of the colony forming units per milliliters (UFC•mL-1)
In the SSF dynamic of the post-harvested wastes of S. tuberosum, inoculated with the microbial preparation, the inclusion of 25 % of the different fibrous materials showed interaction between the evaluated indicators and the fermentation time (P < 0.0001) (tables 5, 6 and 7).
The fermentative indicators pH, concentration of NH3 and organic acids (table 5) had a similar performance to those observed with the inclusion of 15% of the fibrous material, except for the lactic acid. This indicator increased with the time, and was high when alfalfa meal was used (11. 01 mmol/L).
Table 5 Effect of the inclusion of 25% of the fibrous plant material in the pH, NH3 and lactic acid in the solid fermentation of post-harvested wastes of S. tuberosum,inoculated with microbial preparation
| Indicators | Time (h) | Fibrous plant material (25%) | SE ± Sign | ||
|---|---|---|---|---|---|
| Wheat bran | Alfalfa meal | Rice meal | |||
| pH | 0 | 6.85 h | 6.33 f | 6.63 g | 0.045 P<0.0001 |
| 24 | 6.12 e | 6.30 f | 5.87 d | ||
| 48 | 4.91a | 5.22 b | 5.63 c | ||
| NH3 meq.L-1 | 0 | 2.96 a | 3.74 c | 3.05 b | 0.003 P<0.0001 |
| 24 | 4.57 d | 6.34 h | 5.14 e | ||
| 48 | 5.59 f | 6.73 i | 5.81 g | ||
| Lactic acid mmol.L-1 | 0 | 0.002 a | 0.002 a | 0.002 a | 0.003 P<0.0001 |
| 24 | 0.002 a | 0.002 a | 0.002 a | ||
| 48 | 10.02 a | 11.01 c | 9.13 b | ||
a, b, c, d, e, f, g, h, i Means with different letters show differences to P < 0.05, according to Duncan (1955)
Table 6 shows that the inclusion of 25% of the fibrous plant materials favors the fermentative process with wheat bran and rice meal, in accordance with the CP values. However, in all cases there was TP decrease in the time, probably due to the dilution effect of the plant fibrous inclusion, and to a proteolytic and desaminative activity produced by the microorganisms that were established during SSF process. At the same time, this, is show in the increase of ammonia concentration (table 5), even with low values, as well as in the case of the produced lactic acid.
Table 6 Effect of the inclusion of 25 % of the fibrous plant material on the performance of chemical indicators during the solid fermentation of the post-harvested wastes of S. tuberosum, inoculated with the microbial preparation.
| Indicators, % | Time, h | Fibrous plant material (25 %) | SE ± Sign. | ||
|---|---|---|---|---|---|
| Wheat bran | Alfalfa meal | Rice meal | |||
| CP | 0 | 27.24 e | 22.73 a | 24.57 c | 0.296 P<0.0001 |
| 24 | 26.42 de | 23.51 ab | 24.36 bc | ||
| 48 | 29.97 f | 23.18 a | 25.79 d | ||
| TP | 0 | 20.37 f | 16.32 d | 17.29 e | 0.152 P<0.0001 |
| 24 | 16.65 d | 14.47 b | 14.42 b | ||
| 48 | 17.38 e | 15.73 c | 13.81 a | ||
| DM | 0 | 82.60 i | 80.86 h | 79.28 g | 0.012 P<0.0001 |
| 24 | 69.96 d | 70.70 e | 64.61 b | ||
| 48 | 65.38 c | 75.80 f | 62.52 a | ||
| NDF | 0 | 62.71 i | 59.61 g | 53.98 e | 0.013 P<0.0001 |
| 24 | 52.63 d | 58.42 f | 50.54 c | ||
| 48 | 50.34 b | 50.16 a | 62.40 h | ||
| ADF | 0 | 16.13 e | 41.89 i | 8.91 c | 0.014 P<0.0001 |
| 24 | 16.96 f | 25.97 h | 8.33 b | ||
| 48 | 10.13 d | 23.44 g | 7.46 a | ||
| Cell content | 0 | 37.29a | 40.39b | 46.02c | 0.010 P<0.0001 |
| 24 | 47.37b | 41.58a | 49.46c | ||
| 48 | 49.84c | 49.66b | 37.60a | ||
| Hemicellulose | 0 | 46.58c | 17.72a | 45.07b | 0.020. P<0.0001 |
| 24 | 26.66a | 41.46b | 42.21c | ||
| 48 | 40.21b | 26.72a | 54.94c | ||
a, b, c, d, e, f, g, h,i Means with different letters show differences to P < 0.05, according to Duncan (1955)
The relation true protein with respect to crude protein, at 48h, is high for the alfalfa meal (67.86 %) and the wheat bran (57.99%) and, in low amount, for the rice meal (53.54 %). However, in the characteristics of the final fermentation with alfalfa meal there was high consistency, which is expressed in the dry matter (75.80 %), besides the pleasant odor and of other organoleptic characteristics that there were not in the rest and there were only qualitatively recorded.
Nkosi et al. (2015) evaluated the quality of a silage made with potato wastes, and inoculated with LAB, that was supplied to male sheep fed with alfalfa hay. These authors observed increase in protein, fiber decrease and increase in the animals digestibility. In addition, the drying material used improves the dry matter content of the silage. This performance is similar to those occurred in this study with the incorporation of the different raw matters, which acts as drying materials in the food, and considerably improves the DM content at 48h.
In this study, at 48h, there were differences in the DM of 17.22, 5.06 and 16.76 percentage units in wheat bran, alfalfa meal and rice meal, respectively, with relation to the fermentation beginning. This shows that the wheat bran and rice meal have higher involvement in the proteolysis and desamination process by the microbiota present in the fiber and the one that is added with the microbial preparation. In the alfalfa meal, this effect is lower with higher consistency, due to the high relation found of crude protein and true protein.
The previous explained could be associated to those expressed in many studies, where it refers that in the SSF processes the nutritional quality (Zhou et al. 2019 and Van et al. 2019) varies according to the post-harvested wastes used. This could be related with the potato crop technologies, soil (Motalebifard et al. 2013) and climate (Ngobese et al. 2017), among others.
The performance of the cell content and hemicellulose was similar to those observed with the inclusion of 15% of the fibrous materials. However, the NDF performance was different. In this moment, decrease for the wheat bran and the alfalfa meal, while it was focused with rice meal. The ADF, comparing with the initial values, showed marked decrease, but this effect was lower in the rice meal. This coincides with Ramos (2006) and Elías and Herrera (2008) studies, when using corn meal, sweet potato tubers and cassava tubers, as disgregators elements, with those who achieved decrease until 10% of the fibrous component.
Table 7 shows the microbiological analysis of foods with inclusion of 25% of fibrous material. There was not pathogens microorganisms and, the same with 15%, there was important increase of the LAB, especially when the alfalfa meal was used as drying material, which shows superior conditions when improves the humidity content in the food. This performance was showed in the other indicators. Thomas et al. (2013) showed the importance of inoculated with LAB in the elaboration of potato silage. These authors could improve the fermentative indicators and the characteristics of the final food for animal feeding, especially in ruminants.
Table 7 Microbiological analysis of the fermentation of post-harvested wastes of S. tuberosum with the microbial preparation and inclusion of 25% of fibrous material
| Microorganism Log 10 UFC/mL (UFC/mL) | Time, h | Fibrous plant material 25 % | SE ± Sign. | ||
|---|---|---|---|---|---|
| Wheat bran | Alfalfa meal | Rice meal | |||
| Aerobic mesophilic | 0 | 4.96a (9.0x104) | 5.17c (1.4x105) | 5.11 b (1.3x105) | 0.020 P<0.0001 |
| 24 | 5.00a (1.0x105) | 7.92g (8.3x107) | 7.79f (6.2x107) | ||
| 48 | 7.25e (1.8x107) | 7.95g (8.9x107) | 6.91d (8.2x106) | ||
| Yeats | 0 | 4.27e (1.9x104) | 3.90c (8.0x103) | 3.60b (4.0x103) | 0.020 P<0.0001 |
| 24 | 3.99d (9.9x103) | 4.29e (2.0x104) | 1.98a (1.0x102) | ||
| 48 | 5.60g (4.0x105) | 5.68h (4.8x105) | 5.37f (2.4x105) | ||
| LAB | 0 | 5.31c (2.0x105) | 5.00a (1.0x105) | 5.26c (1.9x105) | 0.020 P<0.0001 |
| 24 | 5.15b (1.4x105) | 7.57g (3.7x107) | 6.71d (5.2x106) | ||
| 48 | 6.90f (8.0x106) | 7.88h (7.7x107) | 6.85e (7.1x106) | ||
Means with a common letter are not significant different (P < 0.05)
*Data were transformed according to log10 (X) because they do not follow a normal distribution ( ) means of the colony forming units per milliliters (cfu•mL-1)
The LAB could control the initial period of the fermentation, with the elimination of enterobacteria, clostridia and other microorganisms, with the consequent decrease of the proteolysis and dry matter loss in the fermentation with the excretion of exopolysaccharides. In the active fermentation period could expected a faster action, and lower values that could preserve the protein during the silage, and to contribute to the food digestibility (Muck et al. 2018). In this sense the aspects of more importance are the adequate selection of the strain or mixtures of them (Pardo and Ferrer 2019), the culture medium and the fermentative conditions that allow to obtain high viability level during the process (FAO 2016).
By the previous reasons, the maintaining of the stability and cell viability during the whole process is of great importance for the successful production of biopreparations, when fibrous materials that contributes to the odor, taste, texture and nutritional value of fermented food are mixed.
The results allowed to conclude that the inclusion of fibrous materials in the solid-state fermentation of post harvested wastes of S. tuberosum, inoculated with a microbial preparation, have positive effect on their chemical and microbiological composition. It is recommended, by the quality indicators of the final product, the use of 25% OF alfalfa meal, fermented at 20 °C, during 48h.
