ORIGINAL PAPER

Screening of marine actinomycetes isolated from the Bayof Bengal, India for antimicrobial activity and industrial enzymes

Subramani Ramesh Æ Narayanasamy Mathivanan

Received: 27 March 2009 / Accepted: 2 July 2009 / Published online: 16 July 2009

� Springer Science+Business Media B.V. 2009

Abstract A total of 288 marine samples were collected

from different locations of the Bay of Bengal starting from

Pulicat lake to Kanyakumari, and 208 isolates of marine

actinomycetes were isolated using starch casein agar

medium. The growth pattern, mycelial coloration, pro-

duction of exopolysaccharides and diffusible pigment and

abundance of Streptomyces spp. were documented. Among

marine actinomycetes, Streptomyces spp. were present in

large proportion (88%). Among 208 marine actinomycetes,

111 isolates exhibited antimicrobial activity against human

pathogens, and 151 showed antifungal activity against two

plant pathogens. Among 208 isolates, 183, 157, 116, 72

and 68 isolates produced lipase, caseinase, gelatinase,

cellulase and amylase, respectively. The results of diver-

sity, antimicrobial activity and enzymes production have

increased the scope of finding industrially important mar-

ine actinomycetes from the Bay of Bengal and these

organisms could be vital sources for the discovery of

industrially useful molecules/enzymes.

Keywords Bay of Bengal � Actinomycetes � Diversity �Antimicrobial activity � Extracellular enzymes

Introduction

Marine microorganisms are increasingly becoming an

important source in the search for industrially important

molecules. Today both academic and industrial interest in

marine microorganisms are on the rise, because unique and

biologically active metabolites have been reported from

marine organisms (Jensen and William 1994; Imada 2004;

Zhang et al. 2005). Actinomycetes are present in various

ecological habitats such as soil, fresh water, back water,

lake, compost, sewage and marine environment (Goodfel-

low and Williams 1983). They are considered highly

valuable as they produce various antibiotics and other

therapeutically useful compounds with diverse biological

activities. The vast majority of these metabolites (70%)

have been isolated from actinomycetes with the remaining

20% from fungi, 7% from Bacillus and 1–2% from Pseu-

domonas. Hence, it is known that the actinomycetes are

perhaps the most important group of organisms studied

extensively for the discovery of drugs and other bioactive

metabolites programme (Lange and Lopez 1996; Prabav-

athy et al. 2006).

Marine environment contains a wide range of distinct

microorganisms that are not present in the terrestrial

environment. Though some reports are available on anti-

biotic and enzyme production by marine actinomycetes,

the marine environment is still a potential source for new

actinomycetes, which can yield novel bioactive compounds

and industrially important enzymes (Sharma and Pant

2001). Since late 1980s, the number of novel compounds

isolated from terrestrial microorganisms has steadily

decreased. To cope up with the demand for new pharma-

ceutical compounds and to combat the antibiotic resistant

pathogens, researchers have been forced to look for novel

microorganisms in unusual environment. Relatively, the

Bay of Bengal, an arm of the Indian Ocean has rarely been

explored for microbial diversity and microbial metabolites.

Hence, there is an immense possibility to identify new

marine actinomycetes in the Bay of Bengal to discover

novel bioactive compounds. Accordingly, the present study

S. Ramesh � N. Mathivanan (&)

Biocontrol and Microbial Metabolites Lab, Centre for Advanced

Studies in Botany, University of Madras, Guindy Campus,

Chennai, Tamil Nadu 600025, India

e-mail: prabhamathi@yahoo.com

123

World J Microbiol Biotechnol (2009) 25:2103–2111

DOI 10.1007/s11274-009-0113-4

was aimed to investigate the diversity of industrially

important marine actinomycetes in the Bay of Bengal with

the ultimate objective of discovering novel bioactive

compounds.

Materials and methods

Study area

The study area covered the Bay of Bengal coast of Tamil

Nadu starting from Pulicat lagoon in the north to Kan-

yakumari in the south. This vast area has a variety of niches

such as Pulicat lake, Ennore creek, Chennai harbour and

several estuaries viz., Coovum, Adyar, Palar, Vellar, etc.

Pulicat lake is the second largest brackish water lagoon in

India which runs parallel to the Bay of Bengal. It is located

at 60 km north-east of Chennai and is separated from the

Bay of Bengal by Sriharikota island in Andhra Pradesh

state. The lake is about 360 km2 in size and its depth (water

column) varies from 1 to 6 m. To our knowledge, there is

no report from this lake for microbial diversity. Pichavaram

mangrove is located along the coast of Bay of Bengal with

11�220 N to 11�300 N wide and 79�450 E to 79�520 E long.

The total area of this mangrove is about 1,470 ha con-

sisting of about 50 small islands.

Collection of samples

A total of 80 seashore sediments, 43 seawater samples, 6

marine animals and 5 marine algal samples were collected

from different locations in Tamil Nadu coast of the Bay of

Bengal. Totally 21 mangrove sediments, 6 mangrove rhi-

zosphere sediments and 10 water samples were collected

from Pichavaram and Ennore mangroves in Tamil Nadu.

At least half a kilometer of distance was maintained

between the sampling stations. The sediment samples were

collected at 2–3 m depth using grab sampler. Forty-one

sediments and two brackish water samples were collected

from Pulicat lake, Tamil Nadu at 5–7 m depth by grab

sampler. In addition, 26 deep sea sediment samples, 4 corer

sediments and 39 deep seawater samples were collected

from the Bay of Bengal. The deep sea marine samples were

collected during the cruise programme organized by the

National Institute of Ocean Technology (NIOT), Chennai,

India. A total of four sediments and one water samples

were collected from the estuary of Adayar river and Marina

beach, Chennai, Tamil Nadu. The sediments and water

samples were collected in sterile polypropylene bags and

screw cap bottles, respectively. The collected samples were

brought to the laboratory for isolation of marine actino-

mycetes and the location, nature of sample and pH were

documented.

Measurement of pH

The pH of water samples was measured directly. Ten

grams of each marine sediment sample was suspended in

20 ml of distilled water. It was allowed to stand for 20 min

with intermittent stirring to reach equilibrium. After being

left to settle, the pH was measured.

Isolation of marine actinomycetes

All the marine sediment and seawater samples were sub-

jected to pre-heat treatment prior to serial dilution. Pre-heat

treatment was performed by incubating the seawater and

sediment samples in a water bath at 50�C for 60 min

(Takizawa et al. 1993). Ten grams of sediment samples

were suspended in 95 ml of sterile aged seawater and these

suspensions were considered as 10-1 dilution. Ten milli-

litre of seawater sample was suspended in 90 ml of sterile

aged seawater and these suspensions were considered as

10-1 dilution. Starch casein agar (SCA) medium contained

soluble starch 10 g, vitamin free casein 0.3 g, KNO3 2 g,

NaCl 2 g, K2HPO4 2 g, MgSO4. 7H2O 0.05 g, CaCO3

0.02 g, FeSO4�7H2O 0.01 g, agar 20 g, natural aged sea-

water 1,000 ml, pH 7.0 ± 0.2 was used for isolation of

marine actinomycetes. Serial dilutions were done and

overlaid on the surface of SCA. The medium also con-

tained cycloheximide at 50 lg/ml to minimize fungal

contamination. All the plates were incubated at room

temperature (28 ± 2�C) for 21 days.

The appearance and growth of marine actinomycetes

were observed everyday on SCA plates and the colonies

were recognized by their characteristic chalky to leathery

appearance. Further, they were observed using a light

microscope for their filamentous nature, spores, width of

hyphae and spiral sporophores. Individual colonies were

picked up, and subcultured on SCA and International

Streptomyces Project medium 2 (ISP2) to ascertain their

purity. Various colony characteristics such as size, shape,

mycelial colour, exopolysaccharide (EPS) and diffusible

pigment production were recorded. The pure cultures of

marine actinomycetes were sub-cultured in SCA slants;

incubated at room temperature for 5–7 days to achieve

good sporulation; and then preserved in 20% glycerol vials

at -80�C (Williams and Cross 1971).

Identification of actinomycetes

The cover slip culture technique (Williams and Wilkins

1994) was used to study the morphological characteristics

such as substrate and aerial mycelia, spores in chain and

chain with coil formation, formation of rectiflexibiles, re-

tinaculipetri and spiral spores for all the isolates. In addi-

tion, nature of Gram’s staining, motility and cell wall

2104 World J Microbiol Biotechnol (2009) 25:2103–2111

123

amino acid analysis (Becker et al. 1964) were also deter-

mined to identify the marine actinomycetes isolates up to

genus level.

Growth characteristics of marine actinomycetes

All the isolates of marine actinomycetes were grown on

SCA at room temperature and the growth rate was moni-

tored every day up to 21 days. The isolates, which showed

good growth in 4 days were considered as fast growers and

those that showed good growth between 4 and 7 days were

classified as moderate growers and the slow growers took

more than 7 days for their growth. In addition to growth,

mycelial colour was monitored in all the isolates of marine

actinomycetes and documented.

Screening of marine actinomycetes for antimicrobial

activity

All the 208 marine actinomycete isolates were screened for

antibacterial and antifungal activity by cross streak and

dual culture, respectively. In cross streak method, the

marine isolates were streaked on modified nutrient agar

(NA) (50% NA ? 50% SCA) as a straight line in the left

side corner of the Petriplate and were incubated at room

temperature for 5 days. After incubation, the test human

bacterial pathogens (Staphylococcus epidermidis

MTCC3615, Bacillus subtilis MTCC441, Pseudomonas

aeruginosa MTCC1688, Escherichia coli MTCC1687 and

Candida albicans MTCC227) were streaked at right angle

to the original streak of the actinomycetes isolates. The

zone of inhibition (ZOI) against human bacterial pathogens

was measured after 48 h of incubation. Plates with the

same medium without inoculation of actinomycetes but

with simultaneous streaking of test organisms were main-

tained for controls.

Four marine actinomycete isolates were streaked on

modified potato dextrose agar (PDA) (50% PDA ? 50%

SCA) as straight lines in four corners of the Petriplate and

incubated at room temperature for 5 days. After incuba-

tion, a fresh mycelial disc of fungal phytopathogens (Rhi-

zoctonia solani and Alternaria alternata) was placed in the

center of each Petriplate and the ZOI against phytopatho-

gens was measured after 5 days of incubation. The myce-

lial discs of the test phytopathogens were also kept in

control plates where no actinomycetes were inoculated.

Screening of marine actinomycetes for extracellular

enzymes production

All the isolated marine actinomycetes were screened

qualitatively for the production of five important enzymes

such as lipase, caseinase, gelatinase, cellulase and amylase.

Each actinomycete strain was streaked on the four corners

of the respective substrates such as starch, carboxyl methyl

cellulose, gelatin, casein and tween 20 amended agar plates

separately and was incubated for 5 days at room temper-

ature. Then the plate was flooded with relevant indicator

solution and the development of clear zone around the

growth of organism was considered positive for enzyme

activity.

Results and discussion

Actinomycetes constantly hold a special significance in the

research arena for the past 60 years as the members of this

group, especially streptomycetes, are known to produce a

vast array of compounds with diverse biological properties.

The discovery of new bioactive compounds is a never

ending process to meet the everlasting demand for novel

drug and other biomolecules with antimicrobial and ther-

apeutic properties in order to combat human and plant

pathogens and also to treat other human ailments. In this

scenario, it is more important to identify newer or rare

actinomycetes because they are the pivotal sources of

potent molecules. Marine environment is the biggest res-

ervoir of chemical and biological diversity. Therefore,

research focus on marine environment has been gaining

importance in recent years. However, still it has not been

fully explored and there is tremendous potential to identify

novel organisms with various biological properties. In line

with this view, the present research has been initiated to

identify novel actinomycetes from Indian marine environ-

ment, because its rich microbial diversity has been studied

only to a limited extent. Totally 288 different marine

samples were collected from various locations of the Bay

of Bengal, India (Fig. 1). Among them, a total of 98 acti-

nomycetes were isolated from marine sediments, five from

seawater and nine from marine animals (star fishes, mol-

lusks and sea urchins), but no actinomycetes were isolated

from marine algae. From Pulicat lake samples, 30 actino-

mycetes were isolated from sediments and 13 from

brackish water. From mangrove, 15 actinomycetes were

isolated from sediments, 7 from mangrove rhizospheres

and none of the strains were isolated from mangrove water.

In addition, 18 actinomycete strains were isolated from

deep sea sediments and one strain was isolated from deep

seawater and corer sediments, respectively. A total of

seven actinomycetes were isolated from estuary sediments

and four from estuary water samples (Table 1). Although

soils are considered excellent sources for the isolation of

actinomycetes with diverse potential (Ouhdouch et al.

2001; Lee and Hwang 2002; Prabavathy 2005; Malarvizhi

2006), several actinomycetes have been isolated from

marine samples (Sujatha et al. 2005; Maldonado et al.

World J Microbiol Biotechnol (2009) 25:2103–2111 2105

123

2005; Fenical and Jensen 2006; Ramesh et al. 2006, 2009).

The isolation of actinomycetes from marine sediments was

well documented, yet the proportion of these filamentous

bacteria which represents the indigenous marine microflora

remains unclear. This question persists, in part, because

there is little published information describing the distri-

bution, growth and ecological role of actinomycetes in

marine habitats. As actinomycetes represent a small com-

ponent of the total bacterial population in marine sediments

(Goodfellow and Williams 1983), their role in the marine

environment is difficult to assess. Nevertheless, these

marine actinomycetes are considered economically

important as often they are reported to produce valuable

bioactive molecules and industrially important enzymes

(Jensen et al. 2005b; Ramesh et al. 2009).

In this study, 208 different actinomycetes were isolated

from 288 marine samples using SCA selective medium

prepared in aged seawater. It has already been reported that

the aged seawater amended media were used to isolate and

maintain the marine microorganisms. Although, a number

of selective media (Kuster and Williams 1964; Hayakawa

and Nonomura 1987; Crawford et al. 1993; Duangmal et al.

2005; Jensen et al. 2005a) were developed for isolation of

actinomycetes, SCA was selected, because in this medium

the development of bacterial and fungal colony was very

much suppressed, allowing only the actinomycetes to grow.

Distribution of actinomycetes is influenced by the pH of

the respective environment. In the present study, among the

208 marine actinomycetes, 99 isolates were isolated in the

pH between 8.1 and 8.5, which was followed by the pH

range of 7.6–8.0 from which 92 isolates were obtained.

However, only eight marine actinomycetes were isolated

from the pH range of 7.0–7.5 (Table 2). This is in agree-

ment with the findings of Taber (1960) who demonstrated

that most actinomycetes prefer neutral or slightly alkaline

soils for their growth. Similar to the present results,

Fig. 1 Sampling locations in the Bay of Bengal, India

Table 1 Details of the isolation of marine actinomycetes from the

Bay of Bengal, India

Location Nature of sample No. of

sample

No. of

actinomycetes

isolate(s)

Coastal Sediments 80 98

Seawater 43 5

Macro algae 5 0

Animals 6 9

Deep sea Sediments 26 18

Seawater 39 1

Corer sediments 4 1

Mangrove Rhizosphere sediments 6 7

Sediments 21 15

Water 10 0

Estuary Sediments 4 7

Water 1 4

Brackish lake Sediments 41 30

Brackish water 2 13

Total 288 208

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Malarvizhi (2006) obtained 33% of the actinomycetes from

soils with pH between 7.6 and 8.5. In contrast, Lee and

Hwang (2002) isolated many streptomycetes even from

acidic soil with pH less than 5.0. They also reported the

distribution of other actinomycetes genera such as Micro-

monospora, Dactylosporangium, Streptosporangium, Acti-

nomadura and Nocardioformis in soils at pH 4.0–5.0.

Further, they observed that Streptomyces were predominant

in soils with a pH range of 5.1–6.5.

All the isolated marine actinomycetes were screened for

growth rate on SCA. Surprisingly, among 208 isolates, 151

isolates (72.59%) showed fast growth, 47 (22.59%)

exhibited slow growth and the remaining of 10 isolates

(4.8%) showed moderate growth (Fig. 2). The results

clearly revealed that all the marine actinomycetes are not

slow growing microorganisms and most of their growth is

comparable with filamentous fungi.

Among 208 isolates, 115, 79, 6, 7 and 1 were grey,

white, blue, pink and orange pigmented, respectively.

Interestingly, grey and white mycelial pigmented marine

actinomycetes were prominent in the Bay of Bengal. Fur-

ther, out of 208 isolates, 6 produced diffusible pigment on

SCA agar and 58 isolates produced EPS (Fig. 3). These

pigments and EPS production could be protective mecha-

nisms for actinomycetes to survive in the hostile marine

environment. Ramesh et al. (2006) isolated many EPS

producing and pigmented actinomycetes in the post-Tsu-

nami periods from the Bay of Bengal and most of them

were able to survive for a long period in marine environ-

ment compared to non-pigmented and non-EPS producing

actinomycetes. The adaptation of marine microorganisms

to the diverse marine habitats provides seemingly limitless

evolutionary opportunities for the production of unique

secondary metabolites.

The colonies of actinomycetes were elevated, convex

and powdery in nature. Many of such morphological

characteristics are common in most of the streptomycetes

(Anderson and Wellington 2001; Lo et al. 2002; Fguira

et al. 2005; Sujatha et al. 2005). Most of the marine

Table 2 Potential of marine

actinomycetes isolated from

different pH on antimicrobial

activity and extracellular

enzyme production

pH range Total

isolates

No. of isolates with antimicrobial activity No. of isolates with

extracellular enzymesAgainst human pathogens Against plant pathogens

7.0–7.5 8 3 6 8

7.6–8.0 92 52 76 88

8.1–8.5 99 50 88 96

Total 199 105 170 192

0

50

100

150

200

250

Total isolates Fast Moderate Slow

Growth rate

Num

ber

of is

olat

es

Fig. 2 Growth rate of marine actinomycetes isolated from the Bay of

Bengal

208

1115

6

79

758 6

Total isolates Orange Grey Blue

White Pink EPS Diffusible pigment

Fig. 3 Mycelial colouration of

marine actinomycetes isolated

from the Bay of Bengal

World J Microbiol Biotechnol (2009) 25:2103–2111 2107

123

actinomycetes exhibited different mycelial colourations.

The spore morphology is considered as one of the impor-

tant characteristics in the identification of Streptomyces and

it greatly varies among the species (Tresner et al. 1961). It

has been found that the majority of the marine isolates

produced aerial coiled mycelia and the spores arranged in

chains as already reported by Mukherjee and Sen (2004)

and Roes and Meyer (2005). Further, results of the tests as

outlined in the Bergey’s Manual of Determinative Bacte-

riology (Williams et al. 1989) and the Laboratory Manual

for Identification of Actinomycetes (IMTECH 1998)

showed that among the 208 actinomycetes isolated from

the Bay of Bengal, 183 isolates were identified as Strep-

tomyces spp. and the remaining 25 isolates belonged to

other genera. Remarkably, majority of the marine actino-

mycetes (87.98%) were Streptomyces spp. (Fig. 4). The

cell wall composition is an important criterion for the

identification of Streptomyces (Sujatha et al. 2005) and

chemotaxonomic investigation using isomeric diamino-

pimelic acid (DAP) configuration was already established

(Becker et al. 1964; Lechevalier and Lechevalier 1970). It

has been reported that the streptomycetes are common

inhabitants of marine environments (Kokare et al. 2004a, b;

Fiedler et al. 2005; Ramesh et al. 2006), though other

actinomycetes are also present (Jensen et al. 1991; Mincer

et al. 2002; Magarvey et al. 2004; Maldonado et al. 2008).

The degree of antimicrobial activity varied greatly

among the actinomycetes as shown in Figs. 5 and 6.

Among 208 isolates, 111 isolates (53%) showed high

antimicrobial activity against human pathogens (Fig. 5). Of

which, 31, 18, 52, 81, 28 isolates exhibited antimicrobial

activity against E. coli, P. aeruginosa, S. epidermidis, B.

subtilis and C. albicans, respectively. On the other hand,

four isolates showed antimicrobial activity against all of

the five pathogens, but 97 isolates did not show antimi-

crobial activity. Several researchers have already reported

similar antimicrobial activity of actinomycetes against

various human pathogens. Saadoun and Gharaibeh (2003)

obtained 90 different Streptomyces isolates, of which, 54%

exhibited remarkable antibacterial activity against B. sub-

tilis, S. aureus, E. coli, Klebsiella sp. and Shigella sp.

Deshmukh and Sridhar (2002) isolated several actinomy-

cetes from freshwater coastal stream, of which, four iso-

lates inhibited B. subtilis and E. coli. In addition, Imada

et al. (2007) isolated 100 actinomycete strains from various

locations of the Otsuchi Bay and found that 59 strains

produced antibacterial activity.

In the present study it was recorded that 151 isolates

(72%) showed antifungal activity against plant pathogens.

107 and 98 isolates exhibited antifungal activity against

R. solani and A. alternata, respectively. On the other hand,

54 isolates showed antifungal activity against both the

fungal phytopathogens, but 57 isolates did not exhibit

antifungal activity (Fig. 6). Similarly, Yuan and Crawford

208183

25

Total isolates Streptomycetes Others

Fig. 4 Abundance of streptomycetes in the Bay of Bengal

208

1113118

52

81

284

97

Total isolates Total antimicrobial activity E. coli P. aeruginosaS. epidermidis B. subtilisC. albicans Activity against five pathogens No activity

Fig. 5 Antimicrobial activity of

marine actinomycetes against

human pathogens

2108 World J Microbiol Biotechnol (2009) 25:2103–2111

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(1995) demonstrated in vitro antagonism of Streptomyces

lydicus against various fungal phytopathogens in plate

assay. Further, they observed the inhibition of mycelial

growth in Pythium ultimum and R. solani when grown in

liquid medium with S. lydicus. Kathiresan et al. (2005)

have isolated 160 actinomycetes from various mangrove

environments in India and demonstrated their antifungal

activity against plant pathogenic fungi. Zaitlin et al. (2004)

demonstrated the antagonistic activity of Streptomyces

halstedi and Streptomyces rochei against many phyto-

pathogenic fungi. Search for novel secondary metabolites

with diverse biological activity in assorted environment has

gained greater attention in recent years.

Among 99 marine actinomycetes isolated from the pH

between 8.1 and 8.5, 50 (50.5%) and 88 (88.9%) isolates

exhibited antimicrobial activity against human and plant

pathogens, respectively. Among 92 isolates from the pH

between 7.6 and 8.0, 52 (56.5%) and 76 (82.6%) marine

actinomycetes exhibited antimicrobial activity against

human and plant pathogens, respectively. Among eight

isolates from the pH range 7–7.5, 3 (37.5%) and 8 (100%)

marine actinomycetes showed antimicrobial activity

against human and plant pathogens, respectively (Table 2).

With the growing awareness on environmental protec-

tion, the use of enzymes, particularly from extremophiles,

gained considerable attention in many industrial processes.

In recent years, the microbial enzymes have been replacing

chemical catalysts in manufacturing chemicals, textiles,

pharmaceuticals, paper, food and agricultural chemicals.

Enzyme-based industrial bioprocess now directly competes

with established chemical-based process within the pro-

cessed foods, pharmaceutical and allied fermentation

industries. In the case of terrestrial actinomycetes, many

researchers reported the production of various industrial

enzymes (Mohamedin 1999; Azeredo et al. 2001; Pandhare

et al. 2002; Stamford et al. 2002; Goshev et al. 2005;

Sharma et al. 2005). But to date, it has been concluded that

there are not many reports on the extracellular enzymes

from the marine actinomycetes. However, in this study,

among the 208 isolates, 183, 157, 116, 72, 68 isolates

produced lipase, caseinase, gelatinase, cellulase and amy-

lase, respectively (Fig. 7). Interestingly, 22 isolates pro-

duced all the five enzymes. The majority of actinomycete

strains isolated from the Bay of Bengal produced lipase

followed by caseinase, gelatinase, cellulase and amylase.

Similarly, Leon et al. (2007) isolated many actinomycetes

from marine sediments of the central coast of Peru with

multi-enzyme activity. Notably, a strain among 208 iso-

lates, identified as Streptomyces fungicidicus MML1614,

was able to produce a thermostable alkaline protease

(Ramesh et al. 2009). These results indicated the potential

of marine actinomycetes from the Bay of Bengal for the

208

151107

98

5457

Total isolates Total antifungal activity

R. solani A. alternata

Activity against two pathogens No activity

Fig. 6 Antifungal activity of marine actinomycetes against

phytopathogens

208

183

157

116

68

72 22

Total isolates Lipase Caseinase Gelatinase

Amylase Cellulase Five enzymes

Fig. 7 Extracellular enzymes

production in marine

actinomycetes

World J Microbiol Biotechnol (2009) 25:2103–2111 2109

123

production of various industrial enzymes. Importantly,

majority of the actinomycetes (87.98%) obtained from the

Bay of Bengal produced lipase. The population of lipase

producing actinomycetes is relatively large in marine

environment, because the ocean contains significant

amounts of polymers. Microbes have to produce lipase

enzyme to degrade the polymers in order to adapt in the

extreme environment.

Among the 99 isolates obtained from the pH between

8.1 and 8.5, 96 (97%) marine actinomycetes exhibited

extracellular enzyme production, which is of significance.

Among 92 isolates from the pH between 7.6 and 8.0, 88

(95.7%) showed extracellular enzyme production. How-

ever, all of the eight isolates (100%) obtained from the pH

range of 7–7.5 produced extracellular enzyme (Table 2).

Conclusion

Marine actinomycetes are metabolically active more vig-

orously in the marine environment, which leads to the

production of various enzymes and bioactive compounds

compared to terrestrial strains. Therefore, it is important to

understand the marine-derived actinomycetes in ecological

terms and also as a resource for biotechnology. Our present

study and other reports from our lab (Ramesh 2009; Ra-

mesh et al. 2009) evidently revealed that the Bay of Bengal

is a potential source for a wide spectrum of antimicrobial

and industrial enzyme producing actinomycetes. Moreover,

it can be an imperative resource for bioprospecting novel/

rare Streptomyces spp., which could yield valuable bioac-

tive molecules.

Acknowledgments We thank the Director, CAS in Botany, Uni-

versity of Madras and the Director, National Institute of Ocean

Technology, Chennai for laboratory facilities and organizing the

Cruise programmes, respectively.

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