Synthesis of Poly-γ-Glutamate in Solid-State Fermentation and Its Application in Biocontrol

Authors
Sareh Hashemi 1
Masoud Ahmadzadeh 1
Hossein Saremi 1
Soleiman Ghasemi 2
Azad Omrani Sabbaghi 3
1 Department of Plant Protection, Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj, Alborz, Islamic Republic of Iran.
2 Research and Development Section of Nature Biotechnology Co. (Biorun), Karaj. Alborz, Islamic Republic of Iran.
3 Research and Development Section of Fruit Science Co., Karaj, Alborz, Islamic Republic of Iran.
Abstract
Poly- Gamma- Glutamic Acid (γ-PGA) is a natural polymer with diverse applications across multiple industries. However, its use in agriculture is limited due to high production costs. This study aimed to (1) Optimize the cost-effective production of γ-PGA through Solid-State Fermentation (SSF) using Bacillus velezensis UTB96, (2) Evaluate the concentration and molecular weight of γ-PGA suitable for agricultural applications, particularly in strawberry cultivation, and (3) Explore the impact of γ-PGA on extending the shelf-life of strawberry fruits during cold storage. Initially, the production of γ-PGA using SSF with B. velezensis UTB96 was investigated, along with evaluation of the influence of physicochemical factors on the molecular weight of γ-PGA. Based on the results, three different molecular weights of γ-PGA were identified: 1156.43 kDa, 734.38 kDa, and 296.55 kDa. These were selected for greenhouse trials to assess their effectiveness in controlling gray mold on strawberry plants. The results showed that, by utilizing agricultural wastes including sesame flour, wheat straw, and banana peel in SSF methodology, γ-PGA could be produced at a rate of 70 g/kg of dry weight of the culture medium. Analyzing the impact of γ-PGA on reducing gray mold revealed that this compound could enhance the plant's defense. A significant increase in the activity of ascorbate peroxidase and Phenylalanine Ammonia-Lyase (PAL) enzymes was observed, along with the production of polyphenolic compounds such as ellagic acid. Consequently, these mechanisms improved the plant's flexibility and tolerance to the fungus, helping to maintain the quality of the fruits during cold storage.

Keywords

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Journal of Agricultural Science and Technology
Volume 28, Issue 2
March and April 2026
Pages 415-428