Co-culturing potassium-solubilizing bacteria in a common liquid medium for the development of a consortium fertilizer formulation

Xuyen Thi Vo¹, Mi Kieu Thi Ngo², Nam Duc Truong³, Thao Van Ho⁴ and Nhut Nhu Nguyen^2,3
1 Faculty of Applied Technology, Van Lang School of Technology, Van Lang University, Ho Chi Minh City, Vietnam
² Gia Tuong Company Ltd., Binh Duong branch, Ho Chi Minh City, Vietnam
³ Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
⁴ Office of Soc Trang Provincial People’s Committee, Department of Agriculture – Tai Nguyen, Vietnam

Abstract

Vo, X. Th., Ngo, M. K. Th., Truong, N. D., Ho, Th. V. & Nguyen, Nh. Nh. (2025). Co-culturing potassium-solubilizing bacteria in a common liquid medium for the development of a consortium fertilizer formulation. Bulg. J. Agric. Sci., 31(6), 1155–1165

The co-culture technique is considered one of the approaches for producing microbial biomass for various microbial products. This study employed the method of co-culturing in a standard liquid medium (CLM) to promote the proliferation of potassium-solubilizing bacteria (KSB). KSB strains were screened for solubility index and compatibility on an agar plate, as well as growth rate in a liquid medium. The selected strains of KSB were co-cultured in Luria Bertani broth as CLM. The co-culture efficiency was evaluated based on the cell density of each partner and the total cell density in the broth. Two strains of Enterobacter sp. GTC5.13.1 and Serratia sp. GTC5.19.1 was screened from nine indigenous KSB strains. The ratio of starters and the initial inoculation size had a significant effect on the co-culture efficiency of these two KSB strains. The 4:1 ratio of starters of Enterobacter sp. GTC5.13.1 and Serratia sp. GTC5.19.1 and the initial inoculation size at 0.5 – 1% were suitable for co-culture. Under these conditions, the obtained co-culture exhibited total cell density and solubilization efficiency on mica, kaolin, and feldspar comparable to those of monoculture cultures. Preliminary results proved that the co-culture technique in CLM could be applied to produce biomass of Enterobacter sp. GTC5.13.1 and Serratia sp. GTC5.19.1 for the development of KSB fertilizer.

Keywords: the co-culture technique; common liquid medium; Enterobacter; potassium solubilizing bacteria; proliferation; Serratia
Abbreviations: KSB-potassium solubilizing bacteria; CLM-communal liquid medium; SI-solubility index; SE-solubilization efficiency

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