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A plate assay to screen manganese-tolerant Aspergillus niger strains

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Title A plate assay to screen manganese-tolerant Aspergillus niger strains
 
Creator Singh, Neetu
Punekar, Narayan S
 
Subject Acidogenesis
Mn[II] sensitivity
Strain selection
 
Description 796-800
Two different physiological effects of Mn[II] interactions with Aspergillus niger are known. Excess Mn[II] levels are
toxic and restrict fungal radial growth on plates and second, an Mn[II] limited fungal growth is the key to successful citric
acid fermentation. While studying Mn[II] toxicity we noted that the Mn[II]-supplemented minimal medium (MM) agar
plates were translucent. Also, clearing zones around the fungal colonies owing to organic acid release were observed.
Simultaneous scoring of these two parameters was exploited to screen for Mn[II] tolerant/ insensitive A. niger strains with
improved acid production. Clear halos were best viewed on MM plates supplemented with ≥5.0 mM of Mn[II].
Accordingly, an acid unit (AU; the ratio of diameter of the clear zone to that of colony diameter) was defined. Colonies that
produced larger zones of clearing (and higher AUs) were picked up and sub-cultured. A Mn[II] tolerant/ insensitive
spontaneous mutant of A. niger was isolated by this screen and characterized. It produced significantly higher amounts of
citric acid and the yield was not adversely affected by the added Mn[II]. While separate screens for metal tolerance and
citric acid production were reported earlier, the method presented here is simple and directly combines the two features for
strain selection/screening.
 
Date 2023-10-10T05:52:47Z
2023-10-10T05:52:47Z
2023-09
 
Type Article
 
Identifier 0975-1009 (Online); 0019-5189 (Print)
http://nopr.niscpr.res.in/handle/123456789/62719
https://doi.org/10.56042/ijeb.v61i10.830
 
Language en
 
Publisher NIScPR-CSIR, India
 
Source IJEB Vol.61(10) [October 2023]