Raising the bar in biological formulation : Syensqo’s chassis solutions for solid and liquid formulations

Date:07-10-2024

Céline ORIZET Senior Research Scientist, Europe Syensqo Novecare Agricultural Specialities	Vanessa GOLFETTI Research Scientist, LATAM Syensqo Novecare Agricultural Specialities	Monique ADAMY R&D Formulation Laboratory Manager, Europe  Syensqo Novecare Agricultural Specialities

Formulation Makes the Difference 

In recent years, both environmental and human health concerns have fostered interest in promoting alternatives to synthetic pesticides to control pests and diseases. Biological agents using natural based actives present in the environment such as microorganisms, their metabolites, plant extracts or semiochemicals, provide new control modes of action, complementary to conventional pesticides. 

While biological formulations are considered as one of the most promising tools for sustainable agriculture, remaining challenges, such as limited shelf life or inconsistent biological efficacy in the field, slow down their global adoption rate. 

Several phenomena can explain losses in biological activity: the sensitivity of the microorganisms to various external factors can have an impact at different stages, from storage to application. In this context, optimized formulation strategies are necessary to enhance global bioefficacy of such biopesticides.

In the market today, biological formulations are present in solid and liquid forms. In both cases, the main challenges are to identify suitable co-formulants that do not negatively impact the viability of the targeted beneficial microorganisms. For most microbial categories, it is also important to avoid water in the formulation medium, so as to keep the microorganisms alive, in a dormant stage, preventing premature growth and/or germination before application, and thus maintaining adequate spores viability over extended periods of storage. Another well-known challenge for formulators is that many microbial spores have a strong tendency to agglomerate, as such in the concentrate, or, upon dilution in water. This can cause significant application issues for the end user such as the risk of sedimentation with a sticky deposit in the tank and nozzles clogging issues with delivery devices. Such problems, in turn, generate a lack of biological availability of microbial actives and their metabolites to the targeted surface with, in the end, potential biological efficacy issues. 

In light of those challenges, Syensqo has developed several biological formulations chassis: wettable powders and structured liquid carriers for better biological performances and shelf life extension.

Wettable Powders: overcoming wettability and dispersibility challenges through formulation

Many active ingredients based on microorganisms in the market are formulated as wettable powder (WP). It is a practical formulation type, especially for fungi, with low water activity. However, solid formulations usually cause some challenges upon dilution related to the hydrophobic nature of many fungal spores and their large distribution of particle sizes. This often results in a poor wettability of microbial particles and low suspensibility related to agglomeration, flocculation and/or sedimentation of spores. 

As a result, when making a WP, it is necessary to select high performance, compatible surfactants and polymers with a good adsorption affinity with the targeted actives for wetting agents, dispersants and binders. The formulation process is also very important, and so are the time of mixture and the addition order.

DV AgRHEA™ SA305 is a solid blend solution developed to facilitate the WP formulations of fungi, including wetting agents, co-dispersant and binder. Table 1 shows a typical formulation ratio with this blend. 

Table 1: Example of WP formulation using a fungus. 

The formulation process with DV AgRHEA™ SA305 is very simple, but requires a specific order: first, mixing microorganism, filler and DV AgRHEA™ SA305 and later on, adding Geropon^® TA 72. This sequence guarantees adequate kinetics of adsorption of surfactants in the active.

The physico-chemical parameters of three microbial formulations (Table1), Metarhizium anisopliae (IBCB 425), Beauveria bassiana (IBCB 66). and Trichoderma harzianum (CCT 4790). were determined, showing good results for Wettability (< 2 minutes), suspensibility in low and hard water (higher than 85%) and wet sieve test (with less than 2% of retention), as shown in table 2. 

Table 2: Results tests obtained from the formulation of Metarhizium spp, Beauveria spp and Trichoderma spp. using formulation of Table 1.

The formulation containing DV AgRHEA™ SA305 maintains good viability so far (in progress, superior to 4 months).  

This is an example of what formulation can achieve with the right package selection of surfactants and polymers adapted to three different types of conidia.  

Structured Liquid Carriers, all-in-one solution, for extended shelf life of fungal biopesticides

In terms of liquid formulations, Oil dispersion (OD) are often considered for conidia fungi, since they provide a medium free of water (or with low concentration of water), adequate to favor storage stability. Besides vegetable oil, ready-to-use OD chassis, such as AgRHEA™ OD-EASY, Syensqo has developed structured liquid carriers based on water-miscible polar liquid carriers to suit even the most sensitive fungal biopesticides. An additional benefit of using a water-miscible polar media instead of a nonpolar one is an improved and easier dilution, so that an emulsifying system is not needed.

The structured liquid carriers, DV AgRHEA™ 100 and DV AgRHEA™ 101, ready-to-use solutions, developed by Syensqo contain a polar liquid carrier with low water activity (aw < 0,05 at 25°C), as well as adequate rheological modifier and dispersants.

Figure 1 shows the fungal formulation prepared by mixing 5% of Trichoderma harzianum in 95% of the structured Liquid carrier DV AgRHEA™ 101. Stability test at room temperature and after 12 weeks at 35°C and dispersion test (method adapted from CIPAC MT 41.1 standard according to CIPAC) in CIPAC D water were carried out.

In order to evaluate the shelf life of structured liquid carriers containing fungi, microbial viability studies were conducted on Beauveria bassiana and Paecilomyces lilacinus. 5% of biological products were added in 95% of the structured liquid carriers. Samples of 0.1 mL were taken from each preparation and added to 0.9 mL of an aqueous solution containing 0,1% of Tween 80 to obtain 10-1 dilution. Then, 0,1mL of this dilution was added to 0,9mL to the same aqueous solution successively until the most appropriate dilution was obtained. 0.2 mL of the most appropriate dilutions were spread into petri dishes containing the proper culture media until the colonies grew. Each trial was performed in duplicates and the viability evaluations were performed at 0, 7days, 15 days and monthly. For comparison, a control experiment, with the microbial alone was prepared. The final results were determined through the average of the counts of each microorganism (CFU/mL).

Figure 2: Viability evolution (CFU/mL) of Beauveria bassiana and Paecilomyces lilacinus  in different structured liquid carriers  at 25°C over 10 months.

As shown in the figure 2, the DV AgRHEA™ 100 and DV AgRHEA™ 101 enhance the viability of Beauveria bassiana and Paecilomyces lilacinus compared to the control (microbial alone).

The structured liquid carriers are new formulation basis designed for fungi with extended shelf life, long storage stability and good dispersion upon dilution. Furthermore, DV AgRHEA™ 101 structured liquid carrier can be used to apply microorganisms on seeds before sowing without impacting negatively the seed germination (eg soybean, corn), at recommended dose rate.

Syensqo’s commitment to supporting the sustainable transition of agriculture is at the heart of our development of advanced formulation solutions for Biologicals. Through our innovation efforts, we have developed formulations chassis in solid or liquid form that enhance the stability, efficacy, and user-friendliness of biological products, ensuring they meet the highest standards of performance. Additional technology within Syensqo‘s portfolio, such as AgRHEA™ SticGuard, 100% biobased and biodegradable, are also available, improving the retention, rainfastness and biological efficacy of biopesticides. By answering biological formulators’ main challenges, we strive to accelerate the adoption of biological solutions contributing to a more sustainable future for agriculture, benefiting the environment and society. 

Please do not hesitate to contact us at celine.orizet@syensqo.com

The authors would like to thank Anaïs Marquilly and Elisa Coelho for their contribution to the article.

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