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Original Research Article - (2023) Volume 27, Issue 1

Bacteria of wet-salted Mugil cephalus, Chanos chanos and Gerres oyena (Pisces) from Sudanese Red Sea Coast

Amna M F Mohamed1, Zuheir N Mahmoud2* and Reem A M Ahmed3
 
1Department of Zoology, Faculty of Science, University of Khartoum, Sudan
2Department of Science, Faculty of Education, Red Sea University, Sudan
3Department of Botany, Faculty of Science University of Khartoum, Sudan
 
*Correspondence: Zuheir N Mahmoud, Department of Science, Faculty of Education, Red Sea University, Sudan, Email:

Received: 03-Apr-2023, Manuscript No. ipfs-23-13627; Editor assigned: 05-Apr-2023, Pre QC No. ipfs-23-13627; Reviewed: 19-Apr-2023, QC No. ipfs-23-13627; Revised: 21-Apr-2023, Manuscript No. ipfs-23-13627; Published: 28-Apr-2023

Abstract

Wet-salted Mugil cephalus is occasionally found on shelf. The present study prepared wet-salted M. cephalus, Chanos chanos and Gerres oyena at three salt ratios 15%, 20% and 25%. Preparation covered summer and winter season. Ten bacterial species Microccoccus sp. I, Microccoccus sp. II, Microccoccus sp. III and Microccoccus sp. IV; Staphylococcus sp.; Aerococcus sp.; Microccoccus kristainae, Microccoccus varians, Staphylococcus kloosii and Stomatococcus micococcus. In summer samples of M. cephalus, C. chanos and G. oyena at all brine concentrations and storage durations Microccoccus sp. I, Microccoccus sp. II, Microccoccus sp. III, Microccoccus sp. I, Staphylococcus sp., and Aerococcus sp. were found. In winter samples M. kristainae was found. The frequency of occurrence of M. varians, S. kloosii and S. micococcus followed no consistent pattern. With respect to fresh samples in winter M. kristainae was found in M. cephalus and in G. oyena; and S. kloosii in C. chanos.

Keywords

Bacteria; Wet-salted; Marine; Fish; Sudan

Introduction

Fish is an easily digestible animal protein. Lean fish exhibit high quality protein, minerals and vitamins. Oily fish comprises a rich source of omega 3 and 6 fatty acids well appreciated as health promoter [1]. Fish as a food commodity is rich in amino acids, iodine, selenium, calcium, magnesium, zinc, iron and other minerals [2] and a number of vitamins A, B, B-6, B-12, D, E and K [3]. Fish are found in all water bodies. This explains the growing demand on fish as food [4] Both authors discussed historical consumption and future demand for fish and fishery products for the years 2015/2030. Thus its gross chemical and body weight composition are of significance in nutrition and industry [5].

Studies on microbiology of Red Sea coast brined fish received little attention [6]. reported Vibrio nguillarum, V. parahemolatycum, V. harveyi, V. furnissii, Photobacterium damselae and Tenacibaculum maritmum from the Red sea fishes Siganus rivulatus, Mulloidicthys vanicolensis, Hipposcarus harid, Pterois volitans and Picasso trigger. According to [7] the marine fish Valamugil scheli is mainly used in production of the salted fermented fish Saudi Arabia. The fermented product is dominated by 6 Staphylococcus spp. and 5 Bacillus spp. [8] studied the effect of wet salting method on the quality of salted fish products of Ophiocephalus striatus. The objective of this work is to study the chemical composition of fresh and wet-salted M. cephalus, Chanos chanos and Gerres oyena.

MATERIAL AND METHODS

Fish samples

Highly fresh of Mugil cephalus (n=60), Chanos chanos (n=60) and Gerres oyena (n=60), were purchased from Port Sudan Central Fish Market. Specimens were kept chilled till processed in the laboratory.

Wet-salting

Wet-salting of fish was performed by immersing in brine solution of the desired brine concentration (15%, 20% and 25%). Adequate numbers of tight plastic buckets were used to keep separately the different species at different salt by weight concentration during summer. The same experiment was repeated during winter.

Microbial studies

The standard methods of [9] were used for culturing bacteria in Nutrient Agar and Blood Agar media. Identification and viable counts followed the same author.

Statistical analysis

Paired t-test was used to compare the bacterial count of each species with respect to season. Simple regression analysis was used to correlate total bacterial count and brining time for each species and season[10].

RESULTS

Bacterial species encountered and their frequency of occurrence is given in (Tab. 1.) The table showed that: Ten bacteria species were recorded during this study and abbreviated alphabetically. These with their abbreviations are: Microccoccus sp. I (A), Microccoccus sp. II (B), Microccoccus sp. III (C) and Microccoccus sp. I (D); Staphylococcus sp. (E); Aerococcus sp. (F); Microccoccus kristainae (G), Microccoccus varians (H), Staphylococcus kloosii (I) and Stomatococcus micococcus (J) [11].

In summer samples of M. cephalus, C. chanos and G. oyena at all brine concentrations and storage durations the following bacteria species were found: Microccoccus sp. I, Microccoccus sp. II, Microccoccus sp. III, Microccoccus sp. I, Staphylococcus sp., and Aerococcus sp. The following four species M. kristainae, M. varians, S. kloosii and S. micococcus were not encountered in summer samples [12].

In winter samples of M. cephalus, C. chanos and G. oyena at all brine concentrations and storage durations M. kristainae was found. The frequency of occurrence of M. varians, S. kloosii and S. micococcus followed no consistent pattern. Microccoccus sp. I, Microccoccus sp. II, Microccoccus sp. III, Microccoccus sp. I, Staphylococcus sp., and Aerococcus sp., were not encountered during winter in the three species [13].

With respect to fresh samples in winter M. kristainae was found in M. cephalus and in G. oyena; and S. kloosii in C. chanos.

The 10 bacteria sp. found were not pathenogenic [14].

Total bacterial count

The descriptive statistics of total bacterial count (Tab. 2.) for summer and winter brined M. cephalus, C. chanos and G. oyena showed that:

No bacteria species were encountered in fresh samples of M. cephalus and C. chanos during summer and winter.

For samples of M. cephalus the total bacterial count decreases with increasing brine concentration in summer but increases during winter.

With respect to C. chanos and G. oyena no consistent pattern in total bacterial count in summer and winter brined samples.

The highest mean total bacteria count was 1,411,000 for M. cephalus prepared during winter at 25% brine concentration.

The lowest mean total bacteria count was 72,333 for M. cephalus prepared during summer at 25% brine concentration [15].


Brine con.		 Bacteria spp.
A B C D E F G H I J
Mugil cephalus (Summer samples)
0.0% (Fresh fish) - - - - - - - - - -
15% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
20%, 6 + 3 + 3 + 3 + 3 + 3 + - - - -
25% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
Mugil cephalus (Winter samples)
0.0% (Fresh fish) - - - - - - 1 + - - -
15% - - - - - - 2 + - - -
20% - - - - - - 3 + 1 + 1 + 1 +
25% - - - - - - 3 + - 3 + 1 +
Chanos chanos (Summer samples)
0.0% (Fresh fish) - - - - - - - - - -
15% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
20% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
25% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
Chanos chanos (Winter samples)
0.0% (Fresh fish) - - - - - - - - - 1 +
15% - - - - - - 2 + 1 + 2 + -
20% - - - - - - 4 + - 1 + 2 +
25% - - - - - - 3 + - 3 + -
Gerres oyena (Summer samples)
0.0%  (Fresh fish) 1 + - - - - - - - - -
15% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
20% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
25% 6 + 3 + 3 + 3 + 3 + 3 + - - - -
Gerres oyena (Winter samples)
0.0% (Fresh fish) - - - - - - 1 + - - -
15% - - - - - - 3 + - 2 + 1 +
20% - - - - - - 3 + - 2 + 1 +
25% - - - - - - 1 + 1 + 4 + -

Tab. 1. Frequency of occurrence of bacterial species with respect to fish species,
season, brine concentration. Present (+), Absent (-).


Brine conc.		 Summer season Winter season
Range Mean±SE Range Mean±SE
Mugil cephalus
0.0% (Fresh) 0.0 0.0 0.0 0.0
15% 13,000-350,000 173,500±56,915 300-400,000 122,550±57,566
20% 11,000-180,000 88,167±32,494 300-1,399,999 334,717±213,658
25% 1,000-150,000 72,333±28,970 0.0-8,000,000 1,411,000±1,319,299
Chanos chanos
0.0% (Fresh) 0.0 0.0 0.0 0.0
15% 13.00-35,000 160,500±62,599 12,500-2,000,000 686250±297.772
20% 10,000-230,000 1,121,667±41,393 0.0-400,000 169,999±76,463
25% 7,500-200,000 87,250±33,877 0.0-500.000 170,000±78,230
Gerrus oyena
0.0% (Fresh) 400,000 400,000 500,000 500,000
15% 18,000-350,000 211,333±46,781 14,500-500,000 174,083±78,333
20% 13,000-200,000 123,833±34,574 0.0-4,000,000 868,833±645,777
25% 10,000-250,000 126,667±31,693 0.0-500,000 136,667±78,343

Tab. 2. Mean±SE of total bacterial count for summer and winter prepared brine fish.


Season		 Salt con. Bacterial count at different days
5 10 15 20 25 30 50 90
Mugil cephalus
Summer 15% 3x103 1.8x103 1.5x105 3.5x105 1.8x104 1.3x104 1.2x102 NG
Winter 15% 3x103 1x105 7x104 1.6x103 4x105 6x104 2x102 2x102
Summer 20% 1.8x103 1.5x103 1.5x105 2.5x104 1.3x104 1.1x104 NG NG
Winter 20% 5x103 2x103 1x105 3x102 1.3x105 7x103 5x103 4x102
Summer 25% 1.5x103 1.3x105 1.3x105 1.3x104 1x104 1x103 1x102 NG
Winter 25% NG 8x106 4x104 6x105 4x105 2x104 2x103 2x102
Chanos chanos
Summer 15% 3.5x103 3.5x104 3x105 2.5x104 2.4x105 1.3x104 1x102 1x102
Winter 15% 4.5x103 8x105 5.5x103 12.5x102 8x105 2X106 2x104 1x102
Summer 20% 2x103 3.3x104 1.8x105 2x104 2.3x105 1X104 3x103 2x102
Winter 20% NG 7x104 5x104 4x105 4x105 4x104 1x103 3x102
Summer 25% 1.5x103 1.8x104 1.3x103 1.8x104 2x105 7.5x103 3x102 NG
Winter 25% NG 3x105 3x105 8x104 9x104 5x104 5x102 3x102
Gerres oyena
Summer 15% 3.5x103 1.8x105 3x105 2.2x105 2x105 1.8x104 1.8x102 1x102
Winter 15% 3x103 1.5x104 4x105 1.5x102 5x105 4x104 4x102 3x103
Summer 20% 2x103 1.5x105 2.8x105 1.8x105 1.8x105 1.3x103 1.3x102 1x102
Winter 20% NG 4x106 5x103 2x105 2x105 8x103 5x104 3x104
Summer 25% 1.5x103 1.3x105 2.5x105 1x105 1x105 1x104 1x102 NG
Winter 25% NG 5x105 7x105 3x1041.4 2x105 2x104 3x103 2x102

Tab.3. The impact of storage time on total bacterial count

Impact of storage time on total bacterial count

The impact of storage time on total bacterial count (Tab. 3.) revealed that:

There is a general trend of decrease in total bacterial count with increase of storage count in the three species and the different brine concentration.

The bacterial count during summer was less than winter at days 25, 30, 60 and 90.

The regression analysis of total bacterial count (TBC) and storage time (T) in days revealed weak correlation (p<0.40) only in G. oyena as follows:

At 15%, TBC=324,141 – 4,411T (r=0.047).

At 20%, TBC=216,834 – 2,868T (r=0.024).

At 25%, TBC=167,095 – 2,261T (r=0.035).

DISCUSSION

Stated that spoilage of fresh and lightly preserved fish products is caused by microbial action. They found that highly salted fish products may spoil due to the growth of halophilic bacteria or growth of anaerobic bacteria. Traditionally fermented fish products is the resultant of the action of a wide range of microorganisms including Gram positive and Gram negative bacteria [16]. The present study prepared wet-salted M. cephalus, C. chanos and G. oyena at three salt ratios 15%, 20% and 25%. Preparation covered summer and winter season. Ten bacterial species Microccoccus sp. I, Microccoccus sp. II, Microccoccus sp., and Microccoccus sp. IV; Staphylococcus sp.; Aerococcus sp.; Microccoccus kristainae, M. \ varians, Staphylococcus kloosii and Stomatococcus micococcus. In summer samples of M. cephalus, C. chanos and G. oyena at all brine concentrations and storage durations Microccoccus sp. I, Microccoccussp. II, Microccoccus sp. III, Microccoccus sp. I, Staphylococcus sp., and Aerococcus sp. were found. In winter samples M. kristainae was found. The occurrence of M. varians, S. kloosii and S. micococcus followed no consistent pattern. With respect to fresh samples in winter M. kristainae was found in M. cephalus and in isolated fromEgyptian salted fish Micrococcus spp., Bacillus spp., Proteus vulgaris, P. mirabils and Aeromonas liquefaciens [17]. found Micrococcus spp., Pseudomonas spp., Aerococcus spp., and Vibrio spp. from the salt-fermented fishery products. studied wet-salted Mugil cephalus. He identified aerobic bacteria 18 strains of Staphylococcus equorum, 2 strains of Bacillus subtilis subtilis, two strains of Lactobacillus sp., and 1 strains Bacillus subtilis. He also identified 31 halophilic bacteria included 16 strains of Staphylococcus equorum, 10 strains Staph. sp., and 5 strains of Teratogenococcus halophilus. The 36 identified anaerobes were 23 strains of Clostridium bifermentans, 7 strains of Clostridium bifermentans, 3 strains of Clostridium sp., one strain of each of Clostridium butyricum, Clostridium cochlearium and Clostridium sp. reported Vibrio nguillarum, V. Parahemolatycum, V. harveyi, V. furnissii, Photobacterium damselae and Tenacibaculum Maritmum from a number of marine fish species from Hurghada, Egypt [18]. Reported that the marine Valamugil scheli fish is mainly used in production of the salted fermented fish in Saudi Arabia. The fermented product is dominated by 6 Staphylococcus spp. and 5 Bacillus spp. Determination of the microbiological quality of salted and sun dried fish product is important for protecting consumer’s health studied the characteristics of traditionally dry salted fish product collected from West Nile Region of Uganda and found that E. coli can be used to determine and estimate the microbial quality [19]. Found that salt fermentation resulted in significant (p<0.05) reduction in the total Staphylococcus spp., Micrococcus spp. and yeast mould count for salted freshwater Hydrocynus forskalii. According to studies the fermentation process yielded amines, acetic acid and lactic acid which are responsible for the characteristic odour of the fermented fish and control of spoilage organism’s growth. Thus extends the shelf life of the product. Dry and wet salting is one of the oldest methods of fish preservation. It extracts water from the fish flesh to a level that slow down microbial growth and enzymatic activities [20].

ETHICAL MATTERS

Ethical issues pertaining to approval and consent to participate, human and animal rights, consent for publication, availability of data and materials are Not Applicable.

The authors declare no conflict of interest financial or otherwise.

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