This document discusses microbial biomass production through baker's yeast, single cell protein, and mushrooms. It provides details on the production processes and advantages of each. Baker's yeast is produced through fermentation of molasses and yields 0.4 million metric tonnes annually. Single cell protein production uses alternative waste sources like cellulosic material. Mushrooms are a protein-rich food produced through fermentation of lignocellulose materials and yield environmental benefits.

1. MICROBIAL BIOMASS PRODUCTION –BAKER’S
YEAST ,SINGLE CELL PROTEIN AND MUSHROOM.
PRESENTED BY
M.REVATHI

2. INTRODUCTION
 Yeast cells are small in size (5-8m) ,the density of which reaches
to 1.1g/ml .
 World production of yeast biomass is of the order of 0.4 million
metric tonnes per annum including 0.2 million tones baker’s yeast
alone.
 Yeasts synthesize amino acids from inorganic acids and sulphur
supplemented in the form of salts . They get carbon and energy
sources from the organic wastes ,e .g , molasses , starchy materials ,
milk whey ,fruit pulp , wood pulp and sulphite liquor .
Yield of yeast biomass is greatly affected by many factors similar
to bacteria . Like growth nutrients , organic wastes ,temperature ,
culture , oxygen, etc.

3. FACTORS AFFECTING YIELD OF
BIOMASS
 Like bacteria , growth and yield of yeasts are also affected
by the following factors:
1 .organic substrate and nitrogen ratio ( optimum c:n ratio
favouring high protein content should be between 7:1
and 10:1 .
2. PH of nutrient medium (PH should be in the range of
3.5 to 4.5 to minimize growth of bacterial contaminants).
3. Temperature
(Differs from organism to organism)
Most yeasts have specific growth rate in the range of 300c-
340c
. Some strains also grow in the range of 40- 450c

4. 4. Oxygen (for growth on carbohydrates ) , o2 required
should be 1g/g of dried cells , and for growth on n- alkanes
it should be about 2 g /g dried cells .
5. Maintenance of sterile condition through out the process
and ,
6. Suitable strain of yeast.
7. RECOVERY OF YEAST BIOMASS :
8. Yeast cells (1-2%) growing in fermenter
Decantatin
on
Yeast cells
Centrifugation-I
Yeast cells

5. CONT…..
Centrifugation-II
Yeast cells
Centrifugation-III
Yeast cells
Washing with water ,
Centrifugation-III
Yeast cells (2-1% water)
Vaccum filter
Dry yeast biomass

6. BAKER’S YEAST
 Yeasts are economically the most important group of
organisms .
 For e.g saccharomyces and candida have been associated
with the economic progress .
 The industrially important products of yeast like ethanol ,
which is used as beverage , solvent , chemical feed stock ,
motor fuel , in feed and pharmaceutical purposes.
Elucidation of basic biochemical , setabolic and genetic
processes in living systems .
 Yeast is not only used as a source of protein , but also as
Source of enzymes , vitamins , flavourants ,and also as a
leavening agent.

7.  A good leavening activity of yeast give good yield in dough
fermentation.
(A) Increasing dough volume .
(B) To develop structure and texture .
(C) Impart distinctive flavour and ,
(D) To enhance nutritive value in read and other fermented foods
.
(E) In the parts of central Europe , and also great Britain and USA
,there was a great deal of research into the production and
properties of baker’s yeast with stable characteristics . There
are three types of baker’ s yeast produced commercially ,
namely :

8. (1) Wet compressed yeast (WCY).
(2) Active dry yeast (ADY).
(3) Instant yeast (ITY).
The art of making baker’s yeast using grains were made in
Holland , Germany and Austria during the last country .
CHARACTERISTICS OF BAKER’S YEAST :
The baker’s yeast should have good storage stability , high c:n
ratio , well matured cells , and should impart good spongy
structure in dough by co2 and also flavour .
The yeast must be suitable for aerobic cultivation on molasses ,
grow well and give a good yield as high as 0.567g of yeast per g of
glucose.

9.  The product should have a light colour and fresh smell.
The cells should be separate and of even size .
 They should have a good leavening activity that is not
rapidly lost on storage .
 The genetic stability
 of the strain used must be good and the stock culture must
be stored so that its original properties remain unchanged
.
 The original strain must be stored under conditions ,
where only little growth occurs and must be maintained
by reselection.

10. BAKER’S YEAST PRODUCTION
Diluted and clarified molasses (15% sugars)
Nutrients( N ,P, K, Mg, vitamins)
Molasses medium (PH 4.5)
Fermentation 14 to 16 hrs
Air
Yeast inoculum
Cooling, agitation, pH temperature,
controls and antifoam device
Harvesting by yeast seperator

11. Yeast cream (20% solids)
CONT....
Filtration (Plate and frame
filter press)
Yeast cake (25% solids)
mixing
Protective agents

12. CONT....
Extrusion
Yeast )cakes (500 g
Wrapped in wax paper
Wet compressed yeast
Storage at 40 C
Yeast strands (0.5 to 3.5mm dia)
Drying to 8% moisture
Fill in cans under nitrogen atmosphere
Active dry yeast

13. Refrigerated transport
To bakeries
Storage of ambient/ refrigerated conditions
To bakeries
CONT....
Flow sheet for production of bakers yeast

14. SINGLE CELL PROTEINS
 One approach to produce single cell protein was the use of
petroleum products.
 It is also to some extent effected by the safety considerations ,
needing rigorous testing rather emphasis has been shifted
towards animal feed than developing human food.
 The alternative sources like cellulosic material , food processing
waste or other such material for production of single cell
proteins is being encouraged.
 Use of techniques like solid state fermentation in production
of protein enriched foods or the enzyme which could be used
for bioconversion , has successfully been made.

15.  Extraction of protein from non- conventional sources like
wine lees e.g could become a source of protein compared to
that obtained from conventional sources like fish , oil , seeds
and leaves .
 MUSHROOMS AS A SOURCE OF PROTEIN :
 Mushrooms are fruiting bodies of certain Basidiomycetous
fungi .
 Mushrooms with pleasant flavour and high protein content
are consumed directly as food in the form of soup ,curry
with meat .
 Basidiomycetes or mushroom type fungi have the ability to
degrade lignocellulose material like wood , straws , sawdust
and rice bran .

16.  The cultivation of edible mushrooms is one of the examples
of a microbial culture in which the cultivated organism itself
is a macroscopic , highly developed umbrella like structure ,
directly utilized as human food .
 PRODUCTION OF MUSHROOM :
 The production of mushroom is a fermentation process where
the lignocellulose material is composted with suitable
ingredients (like animal manures and other organic nitrogen
compounds ) over a specific time , the final product is a unique
substrate utilized by the spores present in the inoculum
(spawn) to develop into edible mushrooms under certain
requisite conditions that includes sterilization , addition of
insecticides,

17. Maintenance of temperature and humidity , etc.
The production of mushroom carries several advantages;
few of them are as follows ,
1. Their process of production is simple and easy .
2. Low cost substrates are utilized for their production .
3. Edible mushrooms are rich sources of protein .
4. During the process of cultivation of mushrooms , the
plant residues and waste lignins are converted to useful
edible material .
5. Mushroom protect the enviornment from lignin derived
pollutants.

18. THANK YOU