MICROBIAL GROWTH Microbial grow only if their environment

is suitable. If it is not optimal, growth may occur at

a lower rate or not all, may die, depending on species and condition.

Microbial growth occur in response to the environment.

the physical and chemical environment are essential requirements for microbial growth.

PHYSICAL ENVIRONMENT

1. Effect of Temperature2. Effect of Mechanical3. Effect of Water Activity4. Effect of pH

1. Effect of Temperature In general micro-organisms will grow over a

temperature range of 25 - 30 oC. However, in the environment, micro-organisms can

grow at temperatures below 0oC and above 90 oC although the primary requirement is liquid water.

The vegetative of most bacteria and fungi are killed at temperature around 60 oC within 15-20 min,

yeast and fungal spore are killed only above 80oC, Microbial growth rate, as all chemical reaction, is a

function of temperature. while bacterial spore need about 15-20 min at 121

oC.

2. Effect of Mechanical As a basic operation of fermentation, stirring can

be carried out mechanically, pneumatically or hydro dynamically.

The function of stirring is: the dispersion of the entering and rising bubbles of air, the homogenous mixing of the nutrient medium, the production of sufficiently high turbulence for the heat transfer.

Effect of agitation rate from many researcher show that the optimal condition was obtained at range 100 - 200 rpm.

To prevent cell damage or prevent aeration, only low agitator speed (50rpm) was operated and low oxygen input is possible, therefore anaerobic process can be maintain.

3. Effect of Water Activity Water is important for the cell, 80 % more of the

micro-organism mass is water. During growth. nutrients and waste products enter

and leave the cell, respectively in solution, hence micro-organism can grow only on materials which have adequate free water.

All activity it need water within liquid form. If the water could crystallise or chemical bounded in glucose or salt solution, it can not be utilised by micro-organism. The total of water in the solution refers as water activity.

Pure water have value aw = 1.0 . The type of micro-organism for growth need some the different water. The bacteria generally grow only in medium with aw = 0.91, yeast with aw = 0.78 - 0.81 and fungi aw = 0.80 - 0.87.

Inhibitory levels of substrates vary depending on the type of cells and substrate.

Glucose may be inhibitory at concentrations above 200g/l, probably due to a reduction in water activity

4. Effect of pH

Most bacteria grow best at or near pH 7 (neutral), and the majority can not grow under strongly acidic or strongly alkaline condition.

They do not grow well (<5 and>8,5) exceptions for Acetobacter and sulfur oxidizing bacteria

Hydrogen ion concentration (pH) affects the activity of enzymes.

Yeast will grow over the range 3.5 to 7.5 (grow well at 3-4)

Mold will grow over the range 3. to 8.5 (grow well at 6-7)

•CHEMICAL ENVIRONMENT

1. Effect of Carbon Source2. Effect of Nitrogen Source3. Effect of Dissolved Oxygen

1. Effect of Carbon Source As on chemical reaction rate, The growth rate

depend on the concentration of chemical nutrients.

The relationship of substrate concentration with specific growth rate was given by Monod Equation

where and max are specific and maximum specific growth rate (h-1),S is concentration of substrate (g/l) and Ks is Michaelis-Menten constant.

m

s

S

K S

1. Effect of Carbon Source The concentrate of glucose or salt solution can

cause osmoticlysis in the cell of micro-organism, water will pass in through the cell membrane and out from the cell and it will death.

High substrate concentration that are significantly above stoichiometric requirements are inhibitory to cellular function.

Inhibitory levels of substrates vary depending on the type of cells and substrate.

Glucose may be inhibitory at concentrations above 200g/l. probably due to a reduction in water activity .

2. Effect of Nitrogen Source

Nitrogen (N) is second to carbon in terms of quantity and economic importance.

It consist approximately 10 % of the dry weight.

It serves as the building block for the syntheses of proteins and other cellular macro-molecules.

Ammonia gas and solution is popular in the industry assure of nitrogen because it is inexpensive and easy to use.

Other sources of nitrogen in fermentation media include corn steep liquor, fish meal, yeast extract, and protein hydrolysate .

UNTUK PERTUMBUHAN LACTOBACILLUS

PEPTON 10 g MEAT EXTRACT 10 g YEAST EXTRACT 5 g GLUCOSE 2O g TWEEN 80 1 ml DIKALIUM HIDROGEN PHOSPHAT 2 g SODIUM ACETAT 2 g DIAMMONIUM CTRAT 5 g MAGNISIUM SULPHAT 0.2 g MANGAN SULPHAT 0.05 g DISTILLED WATER 1000 ml

(UTK MEDIA AGAR DITAMBAH 15 g agar)

3. Effect of Dissolved Oxygen

Some micro-organism need oxygen for growth. Micro-organism which must have oxygen for

growth are called “ strict “ or “ obligate “ aerobes.

Strict or obligated anaerobes grow only when oxygen is absent ; these organism occur in river mud and in the rumen.

Microorganisme which normally grow in the presence of oxygen but which can still grow under anaerobic condition (absence of oxygen) are called facultative anaerobes.

Similarly, those which normally grow anaerobically but which can grow in the present of oxygen are called facultative aerobes.

3. Effect of Dissolved Oxygen

For all organism, including obligate aerobes, oxygen may be toxic at any concentration.

The mechanism of oxygen toxicity is through the formation of single oxygen, superoxida radicals O2-, peroxida O2

2– or hydroxy free radical OH- which are destructive to many cell component.

STERILISASICara Alat/Kondisi/Bahan Bahan yang

diseteril1 Pemanasan Basah

(uap)Autoklaf/ 15-40 menit suhu `121 oC

Larutan Pekat, alat kaca, dan plastik

2 Pemanasan Kering

a. Pemanasan Lngsung Api bunsen Kawat ose

b. Pemanasan Tidak Langsung

Oven/60-90 menit suhu 160oC

Alat-alat gelas, bahan padat

3 Pasturisasi (pemanasan)

30 menit suhu 62 oC Makanam damn Minuman

STERILISASI

Cara Alat/Kondisi/Bahan Bahan yang diseteril

4 Tindalisasi (pemanasan)

30 menit suhu 100oC berkali-kali

Media fermentasi

5 Kimia Formaldehid, alcohol, hidrogen peroksida, Lysol,merkuri chloride, ethylene oksida, halogen

Alat gelas, ruangan, bahan yang tidak tahan panas

6 Radiasi Lampu UV Plastik, Petri dish dll.

7 Filtrasi Kapas/ filter Cairan, Udara /gas

Kurva Pertumbuhan Mikroorganisme

1. Lag phase, 2. Exponential phase, 3. Logarithmic phase, 4. Stationer phase and 5. Death phase