1. Introduction
Aquaculture is a fast-growing industry that supplies human society with high-quality proteins [
1]. Rainbow trout is one of the most economically important species in this industry. According to the latest global statistics for 2019, the global production of rainbow trout was 940,000 tonnes, an increase of 21% compared to 2015. As reported by the FAO in 2020, the production of rainbow trout in Iran doubled from 2010 to 2019. In 2019, Iran produced about 206.050 tonnes of rainbow trout, which accounts for 22% of the global production of this species [
2]. The rainbow trout is among the most extensively researched species of fish. Their evolution includes a relatively recent event of tetraploidy, leading to a high frequency of gene duplication. This genetic variation could possibly enhance their ability to adapt [
3]. In the field of aquaculture, infectious diseases caused by bacteria, viruses, and parasites present substantial challenges. Antibiotics are frequently used to treat and prevent bacterial infections in fish. However, excessive antibiotic usage can lead to the development of antibiotic-resistant bacteria, which poses risks to both fish and human health. Consequently, addressing this issue promptly is crucial to safeguard public health and promote sustainable aquaculture practices [
1].
Probiotics are living microorganisms that can be beneficial for the health of fish if supplied in sufficient quantities. They are used in aquaculture as an alternative to antibiotics to promote growth, improve feed efficiency and strengthen the immune system of fish. The probiotics identified in aquatic animals are predominantly
Bacillus spp,
Pseudomonas spp,
Micrococcus spp,
Lactobacillus spp and
Vibrio spp [
4,
5]. Probiotics are added to the food or water environment of fish in the form of single or multiple species. They are used to competitively prevent the growth of pathogens and improve the condition of the water. Probiotics work by colonizing the gut of fish and promoting the growth of beneficial bacteria that help maintain a healthy digestive system. They can also help prevent the growth of pathogenic bacteria by producing antimicrobial compounds. The preparation and use of specific probiotics in cold water farms can help to boost the immune system of fish, reduce economic losses due to microbial diseases, reduce incubation time by improving growth and food conversion ratio, and increase survival rate [
6].
Building upon the established understanding that probiotic efficacy in fish is dependent to the strains, their viability, and water environment, this study aimed to identify novel probiotic strains specifically suited for rainbow trout (Oncorhynchus mykiss) aquaculture in Iran. We hypothesized that such strains could enhance fish health and productivity. Through a rigorous sampling and screening process, ten novel isolates exhibiting probiotic potential were identified. To assess their in vivo functionality, two formulations incorporating these strains were evaluated for their effects on rainbow trout growth performance, immune response, liver enzyme activity, immune-related gene expression, and the composition of the gut microbiota.
4. Discussion
Probiotics are a promising alternative to promote the growth and health of various fish species. They are currently being investigated as a possible replacement for the overuse of antibiotics in aquaculture. These beneficial bacteria have been shown to significantly affect the health and growth performance of the host organism [
16]. There is empirical evidence that the inclusion of probiotics in the feed of farmed fish increases disease resistance, reduce susceptibility to stress and enhance overall vitality [
17,
18]. In the current study, we conducted a screening of probiotic bacteria from the gastrointestinal tract of rainbow trout. In the initial phase of the experiment, the isolated strains were both Gram-positive and catalase-negative. Considering various factors such as bile and acid tolerance, hemolytic and antibacterial activity, attachment to caco2 cell line and antagonistic test, five strains of
P. sp P15,
L. lactis ml3,
W. cibaria ml6,
E. faecium E10 and
L. curvatus 13A showed superior performance. The vast majority of the immunomodulatory probiotic bacteria are Gram-positive lactic acid bacteria. These Gram-positive bacteria are promising options for probiotics due to their beneficial properties and their ability to survive in the harsh conditions of the gastrointestinal tract [
19,
20]. Probiotic bacteria must be able to survive in an acidic environment. These bacteria have evolved several mechanisms to survive in an acidic environment. These mechanisms include changes in the pH of the environment, production of acid-neutralizing compounds, changes in membrane fatty acid composition, and activation of stress response systems [
21]. In the context of aquaculture, especially in rainbow trout farms, the isolation of probiotics that can inhibit pathogens is of utmost importance. This is mainly due to the significant economic impact associated with disease outbreaks [
22,
23]. Therefore, the value of such probiotic strains cannot be overstated. Probiotics can prevent disease outbreaks by inhibiting the growth and colonization of pathogenic bacteria in the host organism. In addition, probiotics can improve the host’s immune response so that it is better able to fight off infections, resulting in better health and survival rates of rainbow trout populations.
The evaluation of growth parameters during the feeding experiment showed a significant improvement in the growth performance of rainbow trout. This improvement was particularly observed in fish fed diet containing
P. sp P15,
L. lactis m13 and
W. cibaria ml6 (treatment A) compared to the control group. Although the final body weight of other probiotic treatments was also numerically increased. Previous studies have reported the beneficial effects of dietary supplementation with probiotic bacteria from the genera
Weissella,
Pediococcus and
Lactococcus on rainbow trout [
24,
25,
26,
27]. Kahyani et al. (2021) showed that feeding rainbow trout with diet supplemented with
Weissella confusa at the level of 3×10
7 CFU/g has been led to a significant improvement in growth performance and immunity compared to the control [
25]. Another study by Yeganeh et al. (2021) reported the beneficial effects of
L. lactis subsp. lactis PTCC 1403 on the feed efficiency, immune response, and resistance to
Y. ruckeri infection in rainbow trout [
27]. In this study, the observed increase in growth rate could possibly be attributed to the influence of lactic acid bacteria (LAB) in competitively excluding pathogenic microbes, producing digestive enzymes, providing nutrients or vitamins and improving intestinal structure [
28].
Figure 2 shows the hematological parameters of rainbow trout fed with different treatments. Interestingly, an increase in the number of RBCs and hemoglobin was observed in rainbow trout fed with treatments A and E. Red blood cells in fish play an important role in the immune response. They are involved in the recognition of pathogens, the elimination of pathogens by binding microbial immune complexes, and the production of cytokines or specific signaling molecules in response to pathogens [
29]. In accordance with the present results, previous studies have reported that probiotics can stimulate erythropoiesis, the process by which new RBCs are formed. Since hemoglobin is an important component of RBCs, this could lead to an increase in hemoglobin levels [
30,
31].
In fish species, immunoglobulin M (IgM) fulfils an important function in both the systemic and mucosal immune systems by protecting the internal systems and mucosal surfaces exposed to the environment [
32]. The administration of probiotics has been observed to stimulate the immune system of fish, leading to an increase in the production of antibodies, including IgM [
33,
34]. Consistent with the literature, this research found a remarkable increase in IgM level in the fish subjected to probiotic treatments A and D. This increased IgM level may improve the fish’s ability to fight infections.
The present study was also designed to determine the effects of different probiotic formulations on the activity of certain liver enzymes in the fish intestine. The results showed that alkaline phosphatase (ALP) level was elevated in treatments of E and F compared to the other groups and lactate dehydrogenase (LDH) was profoundly higher in treatment E. Conversely, alanine transaminase (ALT) levels were lower in fish fed treatments of D and E and AST was higher in the control group than others. These results further support the idea that emphasizes the strain-specific effects of probiotics on liver enzyme activity in fish [
34,
35] and microbiome effects on different organs activity such as liver [
36]. Previous studies have shown that two strains of
Lactobacillus plantarum, 426951 and KC426951, improve the growth and immunity of rainbow trout. However, of the liver enzymes, only ALP was elevated in rainbow trout fed strain 426951. Alanine transaminase plays a crucial role in protein metabolism and serves as an important indicator of liver health in fish [
37]. Alkaline phosphatase plays an important role in the immune system of fish. Alkaline phosphatase can dephosphorylate lipopolysaccharides originating from bacteria. This detoxification process can help prevent bacterial translocation and heal intestinal inflammation [
38].
This study demonstrated a significant increase in gut lactic acid bacteria (LAB) counts in fish fed probiotic diets compared to the control group. Notably, treatment A displayed the highest LAB abundance. These findings align with previous research indicating that probiotics can enhance LAB colonization and modulate gut fish microbiome [
39]. However, conflicting evidence exists. Another study reported a lack of probiotic
L. lactis colonization in the host’s intestinal mucosa [
40,
41]. Establishing probiotic colonization within the gut depending to the individual and strains is complex and influenced by intricate molecular interactions, as acknowledged [
41]. Interestingly, our results showed a persistent increase in LAB even two weeks after probiotic withdrawal (days 60-75). This suggests that all probiotic groups, particularly treatment A, may have the potential for transient and colonization of the intestinal mucosa and influence the gut microbiota composition. Furthermore, a numerical increase in gut heterotrophic bacteria was also observed in probiotic-treated rainbow trout, with treatment A again showing the most pronounced effect. Probiotics can modulate mucosal immunity in fish, potentially leading to the proliferation of specific bacterial populations, including heterotrophic bacteria, through mechanisms like stimulating granulocytes and lymphocytes (essential components of cell-mediated mucosal defense) [
37]. Additionally, probiotics may produce compounds that inhibit pathogenic gut organisms, creating a more favorable environment for the growth of beneficial heterotrophic bacteria [
42]. However, further investigation is needed to confirm these potential mechanisms in our specific context.
Probiotics have a multifaceted impact on the immune system. Our results indicated that while the gene expression level of Interferon-γ remained unchanged with the top selected probiotic diet (treatment A), there was a significant increase in the levels of IL-6 and IgT in the fish that consumed the same probiotic-infused diet. The influence of probiotics on immune gene expression can differ based on the probiotic strain used, the dosage administered, the duration of the treatment, and the fish species [
43]. Immunoglobulin T (IgT) is a key player in the immune defense of fish. Beneficial bacteria such as probiotics boost immune response in fish, including the production of antibodies such as IgT. Probiotics administration can rise in the level of IgT and other antibodies in the fish gut mucus. This effect of probiotics is attributed to the’ ability of this bacteria to regulate the gut microbiota. Probiotics enhance the fish’s capacity to ward off pathogens, mitigate disease and stress, enhance water quality, and even promote growth and reproduction [
13,
44]. TNF-α is an inflammatory cytokine belonging to a group of cytokines that stimulate the acute phase response. IL-6 is often upregulated during inflammation, infection or probiotic ingestion and plays a key role in activating the immune response. Conversely, TNF-α, which plays a role in systemic inflammation, can be downregulated as a protective mechanism to attenuate excessive inflammation and potential tissue damage to the host organism [
45,
46].
Figure 1.
Different growth factor of rainbow trout in treated and control groups a: Food conversion ratio, b: Specific growth rate, c: condition factor, d: length and e: weight. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), B: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (500 mg/kg)), C: ( Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (300 mg/kg)); D: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (500 mg/kg)); E: (a commercial probiotic (E) at 300 mg/kg); F: (control group without probiotics).
Figure 1.
Different growth factor of rainbow trout in treated and control groups a: Food conversion ratio, b: Specific growth rate, c: condition factor, d: length and e: weight. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), B: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (500 mg/kg)), C: ( Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (300 mg/kg)); D: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (500 mg/kg)); E: (a commercial probiotic (E) at 300 mg/kg); F: (control group without probiotics).
Figure 2.
Hematological parameter of rainbow trout in treated and control groups; a: Red blood cell, b: mean corpuscular hemoglobin, c: Mean Corpuscular Volume, d: mean corpuscular hemoglobin concentration, e: Hematocrit test, f: Hemoglobin test, g: White Blood Count, h: lymphocyte, i:Neutrophil, j:Eosinophil and k: Monocyte. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), B: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (500 mg/kg)), C: ( Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (300 mg/kg)); D: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (500 mg/kg)); E: (a commercial probiotic (E) at 300 mg/kg); F: (control group without probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Figure 2.
Hematological parameter of rainbow trout in treated and control groups; a: Red blood cell, b: mean corpuscular hemoglobin, c: Mean Corpuscular Volume, d: mean corpuscular hemoglobin concentration, e: Hematocrit test, f: Hemoglobin test, g: White Blood Count, h: lymphocyte, i:Neutrophil, j:Eosinophil and k: Monocyte. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), B: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (500 mg/kg)), C: ( Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (300 mg/kg)); D: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (500 mg/kg)); E: (a commercial probiotic (E) at 300 mg/kg); F: (control group without probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Figure 3.
Biochemical and immune factors in different dietary treatments a: Immunoglobulin M, b: Lysozyme, c: Lactate dehydrogenase, d: Alanine transaminase, e: Aspartate aminotransferase, f: Alkaline phosphatase, g: Total protein and h: Total glucose. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), B: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (500 mg/kg)), C: ( Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (300 mg/kg)); D: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (500 mg/kg)); E: (a commercial probiotic (E) at 300 mg/kg); F: (control group without probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Figure 3.
Biochemical and immune factors in different dietary treatments a: Immunoglobulin M, b: Lysozyme, c: Lactate dehydrogenase, d: Alanine transaminase, e: Aspartate aminotransferase, f: Alkaline phosphatase, g: Total protein and h: Total glucose. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), B: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (500 mg/kg)), C: ( Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (300 mg/kg)); D: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6, E. faecium E10 and L. curvatus 13A at dosage (500 mg/kg)); E: (a commercial probiotic (E) at 300 mg/kg); F: (control group without probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Figure 4.
Intestinal bacterial measurement a: measurement of lactic acid bacteria and b: number of Heterotrophic bacteria. 15, 30, 45, and 60 days following the probiotics administration, and 75 days (15 days post the discontinuation of the probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Figure 4.
Intestinal bacterial measurement a: measurement of lactic acid bacteria and b: number of Heterotrophic bacteria. 15, 30, 45, and 60 days following the probiotics administration, and 75 days (15 days post the discontinuation of the probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Figure 5.
Relative mRNA expression of immune-related genes, a: IL-6, b: TNF-α, c: INF-γ and d: IgT. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), F: (control group without probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Figure 5.
Relative mRNA expression of immune-related genes, a: IL-6, b: TNF-α, c: INF-γ and d: IgT. A: (Pediococcus sp P15, L. lactis ml3, W. cibaria ml6 at dosage (300 mg/kg)), F: (control group without probiotics). Different letters in columns of each plot indicate a statistical difference in mean according to Duncan test (p < 0.05).
Table 1.
Pathogenic bacteria used in antagonistic assay.
Table 1.
Pathogenic bacteria used in antagonistic assay.
Pathogens |
ATCC |
Staphylococcus aureus |
ATCC 25923 |
Bacillus. Cereus |
ATCC 29213 |
Yersinia ruckeri |
PTCC 1888 |
Listeria Monocytogens |
ATCC 13932 |
Pseudomonas aeruginosa |
ATCC27853 |
Escherichia coli (E. coli) |
ATCC 25922 |
Candida albicans |
ATCC 10231 |
Enterococcus faecalis |
ATCC 29219 |
Table 2.
The primers used in this study.
Table 2.
The primers used in this study.
gene |
Accession number |
Primer sequence |
Tm |
Product length in mRNA |
Product length in DNA |
IL6 |
NM_001124657.1 |
CGCTCGTGGTGTTAGTTAAGGG CGGGCTTCTGAAACTCCTCC |
60 60 |
201 |
858 |
TNF
|
NM_001124357 |
TTATGTGCGGCAGCAGCC CCGTCATCCTTTCTCCACTGC |
61 60 |
221 |
843 |
Ig T
|
AY870265 |
GTACTCTGACCATAGACCAGACA TCCTTCTTGGTGTCTTCCTC |
57 55 |
169 |
490 |
INF
|
NM_001160503.1 |
TACCTGAGCTGAGGACACA TCCTGCGGTTGTCCTTCT |
57 58 |
153 |
1600 |
Beta actin
|
EZ908974 |
CCTCAACCCCAAAGCCAACA CGGAGTCCATGACGATACC |
60 57 |
141 |
694 |
Table 3.
The putative probiotic bacterial strains identified in the final stage of the study.
Table 3.
The putative probiotic bacterial strains identified in the final stage of the study.
Tests |
5A |
P3 |
E10 |
P20 |
P37 |
ml3 |
ml6 |
P15 |
P12 |
13A |
ml4 |
m6 |
P8 |
Catalase |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Gram |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
Morphology |
cocci |
cocci |
cocci |
cocci |
cocci |
cocci |
bacilli |
cocci |
cocci |
bacilli |
bacilli |
bacilli |
cocci |
Hemolytic |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
pH3 time 0 |
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
2×107
|
pH3 time 3 |
2×105
|
2×106
|
3×106
|
5×106
|
9×106
|
1×107
|
7.6×106
|
2×107
|
1.6×107
|
4×106
|
2×105
|
6×106
|
1.2×106
|
0.3% bile |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
≥70 |
Attachment |
weak |
good |
weak |
Very good |
Very good |
good |
good |
Very good |
good |
good |
weak |
weak |
good |
Table 4.
The antibacterial activity of isolated strains against various bacteria.
Table 4.
The antibacterial activity of isolated strains against various bacteria.
Strains |
S. aureus |
B. cereus |
L. monocytogens |
S. enterica |
E. coli |
En. faecalis |
P. aeruginosa
|
Y. ruckeri |
C. albicans
|
P37 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
-
|
>2 |
P20 |
>2 |
>2 |
>2 |
-
|
>2 |
>2 |
>2 |
>2 |
- |
10A |
>2 |
>2 |
>2 |
>2 |
- |
- |
-
|
>2 |
-
|
13A |
-
|
- |
>2 |
-
|
-
|
>2 |
>2 |
-
|
-
|
5A |
-
|
-
|
>2 |
>2 |
- |
>2 |
- |
>2 |
- |
P3 |
>2 |
>2 |
>2 |
-
|
-
|
>2 |
- |
- |
- |
ml6 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
- |
m6 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
ml3 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
- |
P15 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
>2 |
P12 |
>2 |
>2 |
>2 |
-
|
-
|
>2 |
- |
>2 |
- |
P8 |
>2 |
>2 |
>2 |
-
|
-
|
>2 |
- |
>2 |
- |
ml4 |
-
|
- |
>2 |
-
|
-
|
>2 |
>2 |
- |
- |
Table 5.
The antibiogram test result for putative probiotic bacterial strain.
Table 5.
The antibiogram test result for putative probiotic bacterial strain.
Antibiotics |
Abbreviated name |
5A |
P3 |
E10 |
P20 |
P37 |
ml3 |
ml6 |
P15 |
P12 |
13A |
ml4 |
m6 |
P8 |
Clindamycin |
CC |
R |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
Tetracycline |
TE |
S |
S |
S |
S |
S |
M |
S |
S |
S |
S |
S |
S |
S |
Ciprofloxacin |
CP |
S |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
Chloramphenicol |
C |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
Penicillin |
P |
M |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
Erythromycin |
E |
R |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
Ampicillin |
AM |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
Streptomycin |
S |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
rifampin |
RA |
R |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
gentamicin |
GM |
S |
R |
R |
R |
R |
S |
S |
S |
R |
R |
R |
S |
R |
fosfomycin |
FO |
S |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
Enrofloxacin |
NFX |
S |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
tylosin |
TY |
R |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
cholestin |
CL |
M |
R |
R |
R |
R |
R |
R |
R |
M |
R |
R |
R |
R |
sultrim |
SLT |
M |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
Florfenicol |
FF |
M |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
S |
Flumequine |
FM |
M |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
R |
Table 6.
Molecular identification of isolates based on partial 16S rRNA gene sequence information.
Table 6.
Molecular identification of isolates based on partial 16S rRNA gene sequence information.
Strain |
Similarity (%) |
Full Name |
GenBank Accession Number |
m6 |
100 |
Weissella confusa m6 |
MZ066823 |
ml3 |
99.09 |
Lactococcus lactis subsp. lactis strain ml3 |
MN947246 |
ml6 |
99.33 |
Weissella cibaria strain ml6 |
MN947228 |
P12 |
99.44 |
Pediococcus sp. strain P12 |
MN120789 |
P15 |
99.37 |
Pediococcus sp. strain P15 |
MN120790 |
P8 |
99.51 |
Pediococcus sp. strain P8 |
MN093396 |
P37 |
97.57 |
Pediococcus acidilactici strain P37 |
MK758075 |
P20 |
98.71 |
Pediococcus acidilactici strain P20 |
MK757969 |
E10 |
90 |
Enterococcus faecium strain E10 |
MK757968 |
13A |
99% |
Lactobacillus curvatus13A |
MK757915 |
Table 7.
Physicochemical indicators in tanks of different treatments.
Table 7.
Physicochemical indicators in tanks of different treatments.
Indicators |
A |
B |
C |
D |
E |
F |
Oxygen (mg/l) |
8.3±0.2 |
8.9±0.2 |
8.3±0.3 |
8.8±0.3 |
8.8±0.3 |
8.8±0.2 |
pH |
7.96±0.5 |
8.05±0.6 |
7.95±0.5 |
8.02±0.7 |
7.96±0.5 |
7.91±0.7 |
EC(μS/cm) |
521.3±7 |
519.3±8 |
498.3±9 |
504.2±7 |
494.6±8 |
498.5±6 |
N-NO2(mg/l) |
0.15±0.08 |
0.18±0.06 |
0.2±0.05 |
0.24±0.05 |
0.2±0.04 |
0.29±0.08 |
N-NH4(mg/l) |
0.42±0.08 |
0.49±0.04 |
0.46±0.05 |
0.48±0.03 |
0.45±0.05 |
0.44±0.08 |
P-PO4(mg/l) |
0.194±0.006 |
0.198±0.004 |
0.190±0.008 |
0.194±0.006 |
0.190±0.009 |
0.181±0.006 |