Secondary Metabolite Production

Content

• General Introduction

• Factors affecting Secondary Metabolite Production

• Strategies to Enhance the Production

Objective

At the end of the
lecture the student will able to:

• Discuss the advantages and production of secondary
metabolite production

• Explain the strategies to enhance the production of
secondary metabolites

• Identify the suitable media for the production of shikonin

Production
of secondary metabolites

• Secondary metabolites derived from primary metabolites, do
not have any role in the growth of the tissues/cells/plant

• Responsible for therapeutic activity

Advantages of Secondary Metabolite:

• Independent of environmental factors such as climate,
geographical and seasonal variations, diseases, microbial contamination etc

• Ensures quality and yield of the product

• Well defined controlled system – facilitate improved
product formation

• Possible to produce novel compounds of commercial value

• Cultured cells can be used to study the biosynthetic
pathways

• Plant cultures are particularly useful in case of plants
which are difficult or expensive to be grown in the fields.

The production time is less and labour costs are minimal

Factors
affecting production of Secondary Metabolite:

Tissue origin genetic character

Culture conditions

Physiological factors

Selection and screening of high yielding strain

i. Tissue origin
genetic character:

• Plant cells are genetically totipotent

• Under proper environmental conditions, any cell may be
induced to produce any substance

• Sec metabolites are present only in specific part of the
plant

• Eg: Tobacco alkaloids present in roots

• Such plant part should be chosen where there is highest
concentration of desired product

ii. Culture
Conditions

• Chemical composition of nutrient media influences the
production of biomass and sec metabolite production

• Balance should be maintained b/n these two

• Excess increase in biomass reduces the yield of desired
products

• Major chemicals that affect biomass are carbohydrates,
nitrogen, potassium, phosphorous, trace elements, vitamins etc

• Plant growth regulators exert a remarkable influence on
production Eg: Gibberellins increase berberine production, but decreases
shikonin production

iii. Physiological
factors

Temperature:
Plays vital role in yield optimization

Eg: At 5 0C alkaloid production increases but reduced at 35
0C

Light: Secondary
metabolite production in cell culture is influenced by photoperiodicity as well
as quality and intensity

Eg: Cardenolide production in D. lanata is greatly
influenced by light as well as intensity Blue light increased diosgenin content
in D Deltoida and rede light decreased

iv. Selection and
screening of high yield strains

• Different species of plant may vary widely in their
biosynthetic abilities

• Selection of high yielding strain helps in optimization of
yield

• Cell clones from better strain should be selected, it can
be achieved by

– Mutagenic techniques

– Radio immune assay (RIA)

– ELISA, etc

Strategies
to enhance the production of Secondary Metabolite:

Addition of precursor

Light intensity

Selection of high yielding strains

Isolation of product

Use of elicitors

i. Addition of
precursors

• Improved metabolite production sometimes may be achieved
by the addition of precursor to the culture media

Eg: (i). Addition of coniferin to Podophyllum hexandrum
improved production of podophyllotoxin by 12.8 fold

(ii). Addition of L-tryptophan to cinchona ledgeriana
cultures enhance the production of quinoline alkaloids

ii. Light intensity:

Light intensity and selective wave length have stimulating
effect

Eg: Blue light increased diosgenin content in D Deltoida and
red light decreased

iii. Selection of
high yield strains

• Major factor in increasing the production of sec
metabolites

Eg: High yielding strain of Catharanthus roseus on Zenk’s medium
results in higher production of vincristine and vinblastine

iv. Isolation of
product:

• For continuous production the metabolites should be
released rather than retained with in the cells

Eg: Addition of silicone products extract the metabolites
without disturbing the culture

v. Use of elicitors

• Elicitors in plant biology are extrinsic, or foreign,
molecules often associated with plant pests, diseases or synergistic organisms

• Elicitor molecules can attach to special receptor proteins
located on plant cell membranes

• These receptors are able to recognise the molecular
pattern of elicitors and trigger intracellular defence signalling via the
octadeconoid pathway

• This response results in the enhanced synthesis of
metabolites and increase resistance to pest, disease or environmental stress

• Elicitors are of 2 types, namely biotic and abiotic

Production
of Shikonin

• Shikonin is napthaquinone red pigment obtained from the roots
of Lithospermum erythrorhizon

• Shikonin is used as antimicrobial, anti-inflammatory, to
treat burns, wounds and also as a dye in cosmetic preparations

• Chemically it is a napthaquinone derivative

• First process for the commercial production of natural
plant product by the cell suspension cultures was developed in Japan

• Two-stage culture process was developed

• Cells are first grown in a growth promoting medium (MG-5)
for 9 days, filtered and pumped to a second vessel in which the M-9 production
medium is added

• Cells are cultured for 14 additional days, after which
they are recovered by filtration, and the shikonin is extracted using n-hexane
followed by hydrolysis with 2% KOH

• Purified by re – crystallization

Summary

• Protoplast –
Cell without a cell wall

• Isolation of
protoplast – Mechanical method and enzymatic method

• Enzymatic method –
Direct method and sequential method

• Cell wall degrading
enzymes – Cellulase, pectinase, macerozyme etc

• Purification by washing and sedimentation method and
flotation method

• Protoplast culture
– regeneration of cell wall on a suitable media

• Protoplast fusion –
Spontaneous and induced fusion

• Secondary
metabolite – Do not have any role in growth

• Independent of environmental factors, well defined system,
ensures quality and yield

• Factors – Plant
tissue genetic character, culture conditions, physiological factors and
selection of high yield strain

• Strategies –
Addition of precursor, light intensity, high yield strain, isolation of product
and elicitors

• Shikonin – Red
dye, Lithospermum erythrorhizon, anti-inflammatory, in cosmetics

• Production –
Two stages, growth medium and production medium

• Process of initiation and development of an organ is
called organogenesis

• Employed in micro propagation from bud and shoot material
and in organ production from callus and suspension cultures

• Roots, shoots and flowers are the organs that may be
initiated from tissue cultures