Agriculture Reference
In-Depth Information
inhibition (mm) is recorded. Each individual experiment should be replicated three
times at different time intervals.
1.5.6 Production of Microphos
The main objective of microphos production strategy is to enhance the survival of
PS organisms during the period between its production and application to the soil
and the rhizosphere it colonizes. The microphos is prepared commonly by adding
flask-grown cultures (small scale) or fermenter-grown broth (large scale)
containing a large population (about 10
8
-10
9
cells/ml) of PSB to finely powdered
carrier followed by a period of incubation. Here, both the evaluation of broth media
at regular intervals for the presence of specific and viable PSB and selection of a
suitable carrier for inoculant preparation are vital. Generally, the microphos pro-
duction involves (i) inoculum preparation, (ii) processing of the raw material and
(iii) mixing of PSM broth with carrier materials and inoculant packaging.
1.5.6.1
Inoculum Preparation
After proper selection of potential PS organisms, high-quality microphos is pre-
pared. For this, the starter PS organisms are first grown in specific medium, for
instance, Pikovskaya/NBRIP medium, in a small capacity (50 ml) flask, and then
the inoculum are transferred to a larger capacity flasks or a fermenter at the rate of
1-5 % of the medium. However, conditions for PS growth in both flasks and
fermenter of different capacities, like the pH of the medium and nutrient supply
(C and N source), must be at the optimal level. Culture should be incubated at
temperature as required by each specific PS bacterium. The broth in flasks or
fermenter should be checked at regular intervals for both contamination and
microbial density. If at any stage the broth becomes contaminated, it should
immediately be discarded. When the bacterial density reaches to 10
9
cells/ml,
culture growing in flasks/fermenter can be withdrawn and added to sterilized carrier
materials. Incorporation of microorganisms in carrier material enables easy han-
dling, long-term storage and high effectiveness of microphos.
1.5.6.2 Processing of Carrier Material
Various types of materials are used as carrier for seed or soil inoculation (Table
1.3
)
to improve the survival and biological effectiveness of inoculants by protecting
bacteria from biotic and abiotic stresses (Malus´ et al.
2012
). Carrier is a delivery
vehicle which is used to transfer live microorganism in a good physiological
condition from an agar slant of laboratory to a seed/rhizosphere (Smith
1992
).
Since a suitable carrier plays a major role in formulating microbial inoculants, the
