Download INTRODUCTION TO MYCOLOGY

MIC 304
BASIC INDUSTRIAL
MICROBIOLOGY
INDUSTRIAL PRODUCTS FROM
MICROBIAL PROCESSES
(SINGLE CELL PROTEIN)
THE HISTORY OF SCP
During World War II, when there were stortages in
proteins and vitamins in the diet, the Germans
produced yeasts and a mould (Geotrichum candidum)
in some quantity for food; this led to the idea to
produce edible proteins on a large scale by means of
microorganisms during 1970s.
Several industrial giants investigated the possibility of
converting cheap organic materials into protein using
microorganism.
Single-Cell Protein (SCP) is a term coined at
Massachusetts Institute of Technology by Prof
C.L. Wilson (1966) and represents microbial cells
(primary) grown in mass culture and harvested for use
as protein sources in foods or animal feeds.
Single Cell Protein
Single Cell Protein (SCP) is not a pure protein but refers to
whole cells of bacteria, yeasts, filamentous fungi or algae.
Contains carbohydrates, lipids, nucleic acids, mineral salts
and vitamins.
Carbon substrates: major substrates used in commercial
SCP production is alcohols, n-alkanes, molasses, sulphite
liquor and whey.
Microbe
% of Protein
Nucleic acid
Bacteria
50-85
10-16%
Yeast
45-55
5-12%
Filamentous Fungi
30-55
3-10%
Algae
45-65
4-6%
Note: Soya beans contain ~ 40% of protein.
Application of SCP
Animal nutrition: fattening calves, poultry, pigs and fish
breading
Foodstuffs area: aroma carriers, vitamin carrier, emulsifying
aids and to improve the nutritive value of baked products,
in soups, in ready-to-serve meals, in diet recipes
Technical field: paper processing, leather processing and
as foam stabilizers.
SINGLE CELL PROTEIN (SCP)
Not a pure protein but refer to the whole cells of
bacteria, yeast, filamentous fungi or algae.
Also contains carbohydrates, lipids, nucleic acids,
mineral salts and vitamins.
Microbes employed include
Bhalla et al. (2007)
Various carbon sources and microorganisms used for SCP
production
Carbon substrate
Microrganism
CO2
Spirulina species
Chlorella species
Liquid hydrocarbons
(n-alkanes)
Saccharomyces lipolytica
Candida tropicalis
Methane
Methylomonas methanica
Methylococcus capsulatus
Methanol
Methylophilus methylotrophus
Hyphomicrobium sp
Candida boidinii
Pichia angusta
Ethanol
Candida utilis
Glucose (hydrolysed starch)
Fusarium venenatum
Inulin (a polyfructan)
Candida sp
Kluyveromyces sp
Molasses
Candida utilis
Saccharomyces cerevisiae
Whey
Kluyveromyces marxianus
Kluyveromyces lactis
Penicillium cyclopium
Spent sulphite waste liquor
Paecilomyces variotii
Advantages of SCP over conventional plant and
animal protein sources
Rapid growth rate and high productivity (algae: 2–6 hours,
yeast: 1–3 hours, bacteria: 0.5–2 hours)
High protein content, 30-80% on a dry weight basis.
The ability to utilize a wide range of low cost carbon
sources, including waste materials.
Strain selection and further development are relatively
straightforward, as these organisms are amendable to
genetic modification.
Process occupy little land area. Ex: Algal culture can be
done in space that is normally unused and so there is no
need to compete for land..
Production is independent of seasonal and climatic
variations.
Consistent product quality.
Disadvantages of SCP
1) Moulds have their limitations due to lower growth rates
and lower protein content.
2) Algae have cellulose in their cell walls which are not
digestible. They also accumulate heavy metals which
may prove harmful to living beings.
3) Since the bacterial cells are small in size and have low
density, their harvesting from the fermented medium
becomes difficult and costly.
4) Bacterial cells possess high nucleic acid content which
may prove detrimental to human beings by increasing
the uric acid level in blood.
→ Additional steps to overcome this problem make the
production costly.
Basic stage for SCP Production
Medium preparation: The main carbon source may require
physical or chemical pretreatment prior to use.
Ex: Polymeric substrates are often hydrolysed before being
incorporated with sources of nitrogen, phosphorus and
other essential nutrients.
Fermentation:
The SCP Production Process
Basic stages irrespective of the carbon substrate or
microorganisms used:
1) MEDIUM PREPARATION
Physical and chemical pretreatment of carbon sources used.
Ex: Polymeric substrates are often hydrolysed before being
incorporated with sources of nitrogen, phosphorus and other
essential nutrients
2)
FERMENTATION
May be aseptically or run as a ‘clean’ operation depending
upon the particular objectives.
The fermentations process were operated at max growth rate
of microorganisms used.
Ex: Solid state fermentation (SSF) = growth of microorganisms
on predominantly insoluble substrate where there is no free
liquid.
The SCP Production Process
(cont)
3) SEPARATION AND DOWNSTREAM PROCESSING
The cells are separated by filtration or centrifugation.
The spent medium may be processed in order to reduce level of
nucleic acids, eg: thermal shock process to inactivate cellular
proteases
Further purification may involved, eg: solvent wash, dehydration.
The SCP Production Process
5 established methods:
1) The Bel Process
2) The Symba Process
3) The Pekilo Prosess
4) The Bioprotein Process
5) The Pruteen Process
Different carbon source, different microbes
used, different in product quality.
The Bel Process
Whey (liquid waste of dairy industry) is used as substrate.
Whey contains approximately 45 g/L lactose and 10 g/L
protein. It is particularly suitable for the production of SCP
using lactose - utilizing yeast.
Ex: Kluyveromyces marxianus.
The Bel process was designed by theBel Industries in
France.
It was developed with the aim of reducing the pollution
load of dairy industry waste, while simultaneously
producing a marketable protein product which is used for
both human and animal consumption.
In this process initially 75 % of the whey proteins are
precipitated.
The Symba Process
The Symba process was developed in Sweden to
produce SCP for animal feed from potato processing
wastes.
A high proportion of the available substrate is starch,
which many microbes cannot directly utilize.
To overcome this problem two microorganisms were
selected that grow in a symbiotic association.
They are the yeasts Saccharomycopsis fibuligera,
which produces the hydrolytic enzymes necessary for
starch degradation and Candida utilis.
Resultant protein rich biomass contains 45% protein.
The Symba Process
The Pekilo process
This process began operating in 1975 and was the first
commercial continuously operating process for the
production of a filamentous fungus.
The process was developed in Finland for the utilization of
spent sulfite liquor, derived from food processing, that
contains monosaccharides and acetic acid.
Supplements of other carbon sources, usually molasses,
whey and hydrolyzed plant wastes were added.
The organism of interest in this process is Paecilomyces
variotii.
This continuous process is operated aseptically and
produces over 10,000 tonnes of SCP a year.
Resulting dried Pekiloprotein containing up to 59 % crude
protein, is used in the preparation of compounded animal
feed
Bioprotein Process
The Bioprotein process was developed in1990s by
gas-based fermentation plant, Norferm in Norway to
produce protein from methane.
There has been a considerable amount of research
‡
into the production of SCP using alkanes as carbon
sources, notably methane and liquid straight chain
hydrocarbons.
This process uses methane rich natural gas as a sole
‡
carbon and energy source for the growth of
Methylococcus capsulatus.
The Pruteen Process
Methanol has several advantages over methane
and many other carbon sources particularly it is
miscible with water and is available in a very pure
form.
Consequently the resultant protein does not have to
undergo purification.
This process uses a methylotrophic bacterium,
Methylophilus methylotrophus, to produce a feed
protein for chickens, pigs and calves, marketed as
Pruteen.
The dried unprocessed product contained 16 %
nucleic acids and over 70 % crude protein.
Commercial Production of SCP from
Hydrocarbons