Research Article | Open Access
R.M. Revathi, Nagarajappa Adivappar , Suresh Patil, H.P. Sudeep and H.C. Swathi
Arecanut Research Centre, University of Agricultural and Horticultural Sciences, Shivamogga – 577204, India.
J Pure Appl Microbiol. 2021;15(3):1393-1397 | Article Number: 6997 | © The Author(s). 2021
Received: 20/04/2021 | Accepted: 24/06/2021 | Published: 31/07/2021

Arecanut is being grown in an area of 2.71 lakh ha in Karnataka and contributes 65 per cent area to the country. Arecanut sheds the leaf sheath and they are widely used for consumption and packing of food in various occasions. The survey was conducted to know the microbial contaminants associated with leaf sheath plates and during the survey visited to 30 plates manufacturing units situated in Shivamogga and Davanagere districts in Karnataka. Randomly collected areca plates were used for laboratory study to know the contaminants. From these, fungal and bacterial contaminants were isolated and identified by cultural, morphological and biochemical studies. The result revealed that Rhizopus stolonifer, Penicillium citrinum, Aspergillus niger, Aspergillus flavus and Trichoderma harzianum and prevalence of Pseudomonas sp. (32×10-6 cfu/ml), Bacillus sp. (19×10-6 cfu/ml), Micrococcus sp. (12×10-6 cfu/ml) and E. coli (4×10-6 cfu/ml) were observed in contaminated plates under laboratory studies. The study concluded that the prevalence of fungi and bacteria may cause deleterious effects on human health is a chance factor. In future, it is required to concentrate on the sterilizing process which may prevent the health hazardous on human beings.


Arecanut sheath plate, contaminants, Human health


Arecanut palm (Areca catechu L.) leaf sheath sheds naturally which have been used as an ecofriendly food serving and filling material for centuries (Kalita et al)1.   Nowadays with modern technology, this natural and rigid material is compressed into different shapes and used to serve and pack food. The micro enterprise units manufacturing plates from areca leaf sheath are concentrated in major arecanut growing districts in Karnataka viz., Shivamogga, Davanagere, Chikkamagalur, Chitradurga, Dakshina Kannada, Udupi and Uttar Kannada. Leaf Sheath goes waste if not properly utilized for making usable commodities which may helps to small and marginal entrepreneurs for better prize (Adivappar et al)2. The prevalence of contaminants in leaf materials may cause food spoilage and also results in reduction in quality (Omidbeygi et al)3. Some of the fungal species are toxic and may produce mycotoxins in food packing and serving material cause a hazard to human health.

Materials and Methods

In present investigation, contaminated plates were randomly collected from 30 plate making units from different places of Shivamogga and Davanagere districts of Karnataka. The main objective of investigation is to find out the contaminants which are present in the plates under in vitro. Contaminated leaf plate samples were chopped into small pieces and it was aseptically surface sterilized by immersing in sodium hypochlorite (1 %) for 30 seconds then poured in a conical flask containing sterile distilled water.

Isolation of bacterial contaminants
The procedure was followed as per serial dilution technique and pour plate procedure were followed to identify the bacterial colonies then plates were kept at 27°C for 24 to 36 hrs. After incubation, the colonies on nutrient agar plate were counted from different dilutions such as 10-6, 10-7. Bacterial morphology was studied microscopically by Gram staining technique and recognized by following biochemical tests.

Biochemical characterization of bacteria
Biochemical tests viz., Gram reaction, KOH solubility, catalase test, starch hydrolysis, gelatine liquefaction, H2S production, protein digestion, ammonia production, methyl red tests were carried out as per the methods described in laboratory guide for Identification of Bacteria (Schaad)4.

Isolation of fungal contaminanats
The samples were taken into laboratory for surface sterilization then made into small pieces and kept for incubation at 27°C for three days. Fungi which are present in the sample were cultured on PDA plates and observed under microscope.

Cultural and morphological characterization of fungi
The randomly collected areca leaf sheath plates were used for microbial studies. A 5 mm diameter disc of sterile cork borer was used to cut the vigorously growing edge of a fresh culture then placed on Petri plates containing medium (PDA). The set of cultured Petri dishes were incubated at 27°C then fungal growth was examined. For morphological studies isolated fungal culture slides were prepared then observed under microscope.


Survey was conducted to know the microbial contaminants associated with leaf sheath plates and during the survey visited to 30 plates manufacturing units situated in Shivamogga and Davanagere districts in Karnataka (Fig. 1, 2). In this study, the contaminated areca leaf plate (Fig. 3) was used for microbial analysis under laboratory condition. Prevalence of fungal contaminats Rhizopus stolonifer, Penicillium citrinum, Aspergillus niger, A. flavus, Trichoderma harzianum were grown in the culture plate (Table 1), among the fungal contaminants most of the samples were contaminated with Aspergillus niger (Fig. 4,5) and A. flavus (Fig. 6,7). Biochemical characters to determine the colonies of bacteria among that highest prevalence were observed in Pseudomonas sp. (32×10-6 cfu/ml) followed by Bacillus sp. (19×10-6 cfu/ml), Micrococcus sp. (12×10-6 cfu/ml) and E. coli (4×10-6 cfu/ml) and following were given in Table 2.

Table (1):
Prevalence of fungal contaminants in areca leaf sheath plate.

SL No.
Fungal contaminants
Rhizopus stolonifer
Dense cottony growth first white then become grey or yellowish brown with spore production
Dolatabadi et al. (2014)
Penicillium citrinum
Shades of green, sometimes white
Visagie et al., (2014)
Aspergillus niger
Black cottony growth
Gams et. al., (1985)
Aspergillus flavus
Granular growth, bright to dark yellow-green
Hedayati et al. (2007)
Trichoderma harzianum
Initially white and downy, later it developing deep green compact mass, look like concentric ring-like zones
Sandoval-denis et al., (2014)

Table (2):
Prevalence of bacterial contaminants in areca leaf sheath plate.

SL. No.
Prevalent contaminants
Bacterial count
(10-6 cfu/ml)
Colony characters


Bacillus sp.
Colonies are rough, opaque, fuzzy white or slightly yellow with irregular edges and circular in shape. Gram positive


Micrococcus sp.
Colonies are circular, yellow, convex and smooth. Gram positive


Pseudomonas sp.
Colonies are large, opaque, flat colonies with irregular margins and distinctively fruity odour. Gram negative


E. coli
Off-white or beige in color with a shiny texture slightly raised colonies. Gram negative


Fig. 1 & 2. Manufacturing units drying the leaf sheath and plates in open condition

Fig. 3. Contaminated sample

Fig. 4 & 5. Cultural and morphological characteristics of Aspergillus niger

Fig. 6 & 7. Cultural and morphological characteristics of  A. flavus


Areca leaf plates were used for microbial analysis under laboratory condition. Biochemical characters determine the colonies of bacteria among that highest prevalence was observed in Pseudomonas sp. (32×10-6 cfu/ml) followed by Bacillus sp. (19×10-6 cfu/ml), Micrococcus sp. (12×10-6 cfu/ml) and E. coli (4×10-6 cfu/ml). Similar studies were carried out by Janaki et al5.  reported that areca leaf sheath plates were easily get contaminated by bacteria when compared to other microbes. In case of fungal contaminats prevalence of Rhizopus stolonifer, Penicillium citrinum, Aspergillus niger, Aspergillus flavus, Trichoderma harzianum were grown in the culture plate, Matan et al6 also identified mold growth on areca leaf sheath such as Mucor dimorphosporus, Penicillium sp., Aspergillus niger and Rhizopus sp. etc. The contaminants are uaually attached on the surface of plates after the process of manufacture in unit under unhygienic condition was resulted the molds could be observed on plates within a week (Nitimongkonchi)7. Lyratzopoulos et al8,  reported that several species of Penicillium are common contaminants on diverse substrates and are called as potential mycotoxin producers. Identification of Penicillium contamination in food is more important where human pathogenic species are rare, however in favorable condition infections leading to mycotic keratitis, otomycosis and endocarditis.  So there is a need to concentrate on sterilization techniques like UV irradiation treatment to avoid any serious health issue on human beings by using different by products of arecanut leaf sheath viz., plates, cups and food packing materials.


Authors are grateful to Director of Research, University of Agricultural and Horticultural Sciences, Shivamogga, India for providing the necessary facilities.

The authors declare that there is no conflict of interest.

All authors listed have made substantial, direct and intellectual contribution to the work, and approved it for publication.


This article does not contain any studies with human participants or animals performed by any of the authors.

All datasets generated or analyzed during this study are included in the manuscript.

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