Humic acid-amended formulation improves shelf-life of plant growth-promoting rhizobacteria (PGPR) under laboratory conditions


Citation

Sadeq, Buraq Musa and Tan, Ali Kee Zuan and Susilawati Kasim and Wong, Mui Yun and Nur Maizatul Idayu Othman and Alkooranee, Jawadyn Talib and Chompa, Sayma Serine and Akter, Amaily and Rahman, Md Ekhlasur (2023) Humic acid-amended formulation improves shelf-life of plant growth-promoting rhizobacteria (PGPR) under laboratory conditions. Pertanika Journal of Science & Technology (Malaysia), 31 (3). pp. 1137-1155. ISSN 2231-8526

Abstract

Plant growth-promoting rhizobacteria (PGPR) is a soil bacterium that positively impacts soil and crops. These microbes invade plant roots, promote plant growth, and improve crop yield production. Bacillus subtilis is a type of PGPR with a short shelf-life due to its structural and cellular components, with a non-producing resistance structure (spores). Therefore, optimum formulations must be developed to prolong the bacterial shelf-life by adding humic acid (HA) as an amendment that could benefit the microbes by providing shelter and carbon sources for bacteria. Thus, a study was undertaken to develop a biofertilizer formulation from locally isolated PGPR, using HA as an amendment. Four doses of HA (0, 0.01, 0.05, and 0.1%) were added to tryptic soy broth (TSB) media and inoculated with B. subtilis (UPMB10), Bacillus tequilensis (UPMRB9) and the combination of both strains. The shelf-life was recorded, and viable cells count and optical density were used to determine the bacterial population and growth trend at monthly intervals and endospores detection using the malachite green staining method. After 12 months of incubation, TSB amended with 0.1% HA recorded the highest bacterial population significantly with inoculation of UPMRB9, followed by mixed strains and UPMB10 at 1.8x10⁷ CFUmL⁻¹, 2.8x10⁷ CFUmL⁻¹ and 8.9x10⁶ CFUmL⁻¹, respectively. Results showed that a higher concentration of HA has successfully prolonged the bacterial shelf-life with minimal cell loss. Thus, this study has shown that the optimum concentration of humic acid can extend the bacterial shelf-life and improve the quality of a biofertilizer.


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Abstract

Plant growth-promoting rhizobacteria (PGPR) is a soil bacterium that positively impacts soil and crops. These microbes invade plant roots, promote plant growth, and improve crop yield production. Bacillus subtilis is a type of PGPR with a short shelf-life due to its structural and cellular components, with a non-producing resistance structure (spores). Therefore, optimum formulations must be developed to prolong the bacterial shelf-life by adding humic acid (HA) as an amendment that could benefit the microbes by providing shelter and carbon sources for bacteria. Thus, a study was undertaken to develop a biofertilizer formulation from locally isolated PGPR, using HA as an amendment. Four doses of HA (0, 0.01, 0.05, and 0.1%) were added to tryptic soy broth (TSB) media and inoculated with B. subtilis (UPMB10), Bacillus tequilensis (UPMRB9) and the combination of both strains. The shelf-life was recorded, and viable cells count and optical density were used to determine the bacterial population and growth trend at monthly intervals and endospores detection using the malachite green staining method. After 12 months of incubation, TSB amended with 0.1% HA recorded the highest bacterial population significantly with inoculation of UPMRB9, followed by mixed strains and UPMB10 at 1.8x10⁷ CFUmL⁻¹, 2.8x10⁷ CFUmL⁻¹ and 8.9x10⁶ CFUmL⁻¹, respectively. Results showed that a higher concentration of HA has successfully prolonged the bacterial shelf-life with minimal cell loss. Thus, this study has shown that the optimum concentration of humic acid can extend the bacterial shelf-life and improve the quality of a biofertilizer.

Additional Metadata

[error in script]
Item Type: Article
AGROVOC Term: Rhizobacteria
AGROVOC Term: Bacteria
AGROVOC Term: plant growth
AGROVOC Term: essential plant nutrients
AGROVOC Term: humic acids
AGROVOC Term: laboratory experimentation
AGROVOC Term: analysis of variance
AGROVOC Term: keeping quality
AGROVOC Term: biofertilizers
Geographical Term: Malaysia
Uncontrolled Keywords: Colony forming unit, formulation, humic acid, PGPR, shelf-life
Depositing User: Ms. Azariah Hashim
Date Deposited: 20 Mar 2025 03:54
Last Modified: 20 Mar 2025 03:54
URI: http://webagris.upm.edu.my/id/eprint/1951

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