Small microcapsules of crystal proteins and spores of Bacillus thuringiensis by an emulsification/internal gelation method

Abstract

This paper describes a microencapsulation process of a spore crystal aggregate produced by Bacillus thuringiensis var. kurstaki HD-1. The methodology is based on the emulsification/internal gelation method, and was implemented to produce microcapsules of small diameter (< 10 μm) with the capacity to protect the spore crystal aggregate from extreme ultraviolet radiation. The diameter of microcapsules was in the range of 3.1 ± 0.2-6.8 ± 0.4 μm, which is considered adequate for biological control purposes. The protective effect of the alginate coat was verified by the remaining 60 ± 2% and 40 ± 1% of spore viability and protein activity, respectively, after UV-B radiation of 236 J, and with bioassays with Spodoptera frugiperda. It is expected that the protective effect of the alginate coat will improve the effectiveness of the Bt-HD1 formulated as small diameter microcapsules, and their yield, once they are released into the environment, will also be improved.

<i>In vitro</i> evaluation of microencapsulated <i>Bacillus thuringiensis</i> exposed to different temperatures against <i>Helicoverpa armigera</i> (Hubner)

“…Our findings are consistent with the experiment carried out by Garica et al (2011) on the microencapsulation process of a spore crystal aggregate generated by B. thuringiensis var. kurstaki HD-1, wherein they reported that the microcapsules' diameter ranged from 3.1 ± 0.2 to 6.8 ± 0.4 µm.…”

“…Similarly, Bashir et al (2016) observed the highest larval mortality 97.9 % for microencapsulated B. thuringiensis kurstaki. Garica et al (2011) experimented with the microencapsulation process of a spore crystal aggregate produced by B. thuringiensis var. kurstak HD-1 and reported 46 % larval mortality of the Spodoptera frugiperda population.…”

Biological Activity of Phytochemicals from Agricultural Wastes and Weeds on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

“…Larvae were reared at 25 ± 2 • C, relative humidity of 80 ± 5%, and 18/6 photoperiod. Dead and surviving larvae were recorded every 24 h for seven days [39]. On the seventh day, the weight (OHAUS Explorer brand analytical balance) and size (Vernier; Scale Regla Dial Caliper mm metric) of the surviving larvae were recorded.…”

pH-Controlled Bacillus thuringiensis Cry1Ac Protoxin Loading and Release from Polyelectrolyte Microcapsules

“…A methodology of microencapsulation was investigated which have the capacity to protect the spore crystal aggregate produced by Bacillus thuringiensis var. kurstaki HD-1 from extreme ultraviolet radiations which are equivalent to 80 and 558 days of sunlight exposure in clear weather in Mexico [23]. These methods have somewhat extended the persistent period; however, the contents of the capsules are released without precise control.…”

“…These methods have somewhat extended the persistent period; however, the contents of the capsules are released without precise control. Part of the insecticidal Cry toxins can be released gradually from the capsules after the pesticides are sprayed into the environment [11], [23]. Therefore, the efficiency of the protection is not satisfactory.…”