UV protectants for the biopesticide based on Bacillus sphaericus Neide and their role in protecting the binary toxins from UV radiation

Ultraviolet protection of Bacillus thuringiensis through microencapsulation with Pickering emulsion method

An encapsulated formulation of Bacillus thuringiensis (Bt) was produced by the Pickering emulsion technique to improve its activity and stability under UV-A radiation. In this technique latex particles, GO nanosheets, olive oil, ethanol, and water were used to encapsulate Bt in colloidosomes. The protective efficacy of this formulation in protecting Bt subsp. Kurstaki against deactivation by UV-A irradiation was measured, so that spore viability and mortality on Ephestia kuehniella (E. kuehniella) Zeller larvae under UV-A radiation are investigated. According to the results of both tests, encapsulated formulation at a concentration of 0.045% has the highest protection of viability. Hence, colloidosome microcapsule formulations successfully provide good protection against UV radiation.

Biopesticide and formulation processes based on starch industrial wastewater fortified with soybean medium

The aim of this study was to produce Bacillus thuringiensis-based biopesticide using starch-producing industry wastewater (SIW) fortified with soybean medium and optimize the formulated product using different adjuvants. This study was necessary as low endotoxin concentration is obtained in formulated biopesticide when SIW alone is used as fermentation medium. The fermentation runs were conducted using SIW alone and SIW fortified with 25% soybean (w/v) medium in 2000 L and 150 L bioreactor, respectively. SIW supplemented with soybean medium showed an increase in cell count (from 1.95 × 108 to 1.65 × 109 CFU mL-1), spore synthesis (from 1.5 × 108 to 1.35 × 109 CFU mL-1) and endotoxin concentration (from 436 to 1170 μg mL-1) when compared to SIW medium alone. The fermented broth was concentrated using continuous centrifugation and adjuvants were added for biopesticide formulation in order to enhance its resistance against UV rays and rainfastness. Entomotoxicity of the formulation produced using fermented broth of SIW fortified with soybean (38,000 IU μL-1) was higher than that obtained by SIW medium alone (21,000 IU μL-1), commercial biopesticide Foray 76B (20,000 IU μL-1) and Btk sander's (12,500 IU μL-1).

Concepts and applications of foliar spray for microbial inoculants

Damages of the (agro)ecosystem by extensive use of chemical fertilizers and pesticides, the global dying of bee populations possibly linked to pesticide spraying, and stricter regulations for pesticide use together with successful use of microbials in IPM programs are pushing on the development and commercialization of new microbial products and a large and growing biostimulants and biocontrol market. This review focuses on microbial inoculants including bacteria, fungi, and viruses used as biostimulant or biocontrol agent for foliar application and covers all important steps from inoculant development to successful field application. Topics presented comprise typical spraying equipment including the importance of the spraying process and relating effects, furthermore formulation development including classification and adjuvants, and thirdly regulatory aspects as currently applied or under discussion. Microbial inoculants for foliar spray reported in scientific literature are summarized and contrasted with selected commercial products. Special attention is given to factors most important in microbial spray: (a) type of active ingredient (bacteria, fungi, viruses), (b) mode of action (ingestion, contact, competition), (c) interaction with the plant leaf surface, (d) droplet size in terms of microbe concentration and leaf coverage, and (e) environmental conditions during spraying. Finally, we want to emphasize that timely administration is of utmost importance for successful spraying and maximum efficacy. This might be supported by weather stations and disease/pest models as an important step towards precision farming.

Microbiome profile of the amniotic fluid as a predictive biomarker of perinatal outcome

Chorioamnionitis (CAM), an inflammation of the foetal membranes due to infection, is associated with preterm birth and poor perinatal prognosis. The present study aimed to determine whether CAM can be diagnosed prior to delivery based on the bacterial composition of the amniotic fluid (AF). AF samples from 79 patients were classified according to placental inflammation: Stage III (n = 32), CAM; Stage II (n = 27), chorionitis; Stage 0-I (n = 20), sub-chorionitis or no neutrophil infiltration; and normal AF in early pregnancy (n = 18). Absolute quantification and sequencing of 16S rDNA showed that in Stage III, the 16S rDNA copy number was significantly higher and the α-diversity index lower than those in the other groups. In principal coordinate analysis, Stage III formed a separate cluster from Stage 0-I, normal AF, and blank. Forty samples were classified as positive for microbiomic CAM (miCAM) defined by the presence of 11 bacterial species that were found to be significantly associated with CAM and some parameters of perinatal prognosis. The diagnostic accuracy for CAM according to miCAM was: sensitivity, approximately 94%, and specificity, 79-87%. Our findings indicate the possibility of predicting CAM prior to delivery based on the AF microbiome profile.

Efficacy of olive mill wastewater for protecting Bacillus thuringiensis formulation from UV radiations

The effectiveness of 10 low-cost UV-absorbers in protecting Bacillus thuringiensis subsp. kurstaki BLB1 toxins against inactivation by UV-A and UV-B irradiation was evaluated in this study. Among them, two by-products, molasses and olive mill wastewater (OMW) were selected for further studies. They were tested at different concentrations of 0.05, 0.1, 0.15 and 0.2% using the para-aminobenzoic acid (PABA) as a common UV protectant. Interestingly, addition of PABA and OMW to BLB1 formulations was found to be most effective in protecting BLB1 spores at 90.8 and 76.4% respectively and in preserving delta-endotoxin concentration at a level of 81.7 and 72.2%, respectively when used at a concentration of 0.2%. The lowest preserved spores (46.3%) and delta-endotoxin level (12.4%) was found using molasses. In contrast, spore count and delta-endotoxin concentration were completely reduced after an exposure of unprotected Bt strain BLB1 to UV radiations up to 96h. SDS-PAGE analysis of protected and unprotected samples revealed that delta-endotoxin bands (130, 65-70kDa) were conserved until 96h of UV exposure in presence of PABA or OMW compared with their disappearance in presence of molasses after 72h of exposure and their dramatically decline from 8h of exposure in unprotected mixture. A complete loss of larvicidal toxicity against Ephestia kuehniella was found after 24h of exposure in absence of any UV-absorber. Addition of OMW or PABA offered the highest levels of insecticidal activity with 63.2 and 74.7% of residual toxicity, respectively. Whereas, molasses addition, as UV protectant retained only 26.3% of residual activity after 96h of exposure. Therefore, addition of OMW by-product to Bt formulation may be a suitable alternative to others synthetic chemical compounds. OMW may also provided added value, be environmentally friendly and less hazardous, when used at low concentration.

Polymeric macroporous formulations for the control release of mosquitocidal Bacillus sphaericus ISPC-8

Bio-polymeric mosquitocidal formulations were developed for the control release of Bacillus sphaericus ISPC-8 by the immobilization of its spore-crystal complex onto the macroporous polymeric matrices. The biodegradable formulations were synthesized at sub-zero temperature using natural polymeric substrates like agarose, alginate, cellulose, non-adsorbent cotton, wooden cork powder and also magnetite nanoparticles. The obtained polymeric matrices were morphologically characterized, which showed 85-90% porosity, uniform pores distribution, high permeability and controlled degradation (19-30%) in 4 weeks depending upon the composition of formulations. Further, the polymeric macroporous formulations were tested for persistence of mosquitocidal activity against Culex quinquefasciatus larvae. Unformulated B. sphaericus ISPC-8 spores retained 54% of larvicidal activity after 7 days, which completely reduced after 35 days of treatment. However, the immobilized B. sphaericus spores in agarose-alginate formulations showed high larvicidal activity on day 7 and retained about 45% activity even after 35 days of treatments. Studies on UV-B and pH dependent inactivation of toxins and spore viability showed that these formulations were significantly protecting the spores as compared to the unformulated spores, which suggest its potential application for the mosquito control program.

The bacterium, Lysinibacillus sphaericus, as an insect pathogen

Since the first bacteria with insecticidal activity against mosquito larvae were reported in the 1960s, many have been described, with the most potent being isolates of Bacillus thuringiensis or Lysinibacillus sphaericus (formerly and best known as Bacillus sphaericus). Given environmental concerns over the use of broad spectrum synthetic chemical insecticides and the evolution of resistance to these, industry placed emphasis on the development of bacteria as alternative control agents. To date, numerous commercial formulations of B. thuringiensis subsp. israelensis (Bti) are available in many countries for control of nuisance and vector mosquitoes. Within the past few years, commercial formulations of L. sphaericus (Ls) have become available. Because Bti has been in use for more than 30 years, its properties are well know, more so than those of Ls. Thus, the purpose of this review is to summarise the most critical aspects of Ls and the various proteins that account for its insecticidal properties, especially the mosquitocidal activity of the most common isolates studied. Data are reviewed for the binary toxin, which accounts for the activity of sporulated cells, as well as for other toxins produced during vegetative growth, including sphaericolysin (active against cockroaches and caterpillars) and the different mosquitocidal Mtx and Cry toxins. Future studies of these could well lead to novel potent and environmentally compatible insecticidal products for controlling a range of insect pests and vectors of disease.

Control of Apple Blue Mold by the Antagonistic Yeast Pichia anomala Strain K: Screening of UV Protectants for Preharvest Application

When applied preharvest, antagonistic yeasts that act as biocontrol agents of postharvest fruit diseases must survive the environmental conditions in the field. In particular, UV-B radiation (280 to 320 nm) can greatly reduce their survival and effectiveness. The influence of artificial UV-B radiation on Pichia anomala strain K, an antagonistic yeast with potential for control of postharvest fruit diseases, was evaluated in vitro and in vivo. The in vitro 50 and 90% lethal dose values were 0.89 and 1.6 Kj/m², respectively, whereas lethal values in vivo were 3.2 and 5.76 Kj/m², respectively. UV protectants tested in combination with strain K included congo red, tryptophan, riboflavin, lignin, casein, gelatine, folic acid, tyrosine, and four mixtures. Riboflavin, folic acid, and the mixtures 1% folic acid + 0.5% tyrosine + 0.5% riboflavin (formula 2), 0.5% folic acid + 1% tyrosine + 0.5% riboflavin (formula 3), and 0.5% folic acid + 0.5% tyrosine + 1% riboflavin (formula 4) reduced yeast mortality caused by UV-B radiation in petri dish assays. Riboflavin, folic acid, gelatine, lignin, and tyrosine reduced yeast mortality caused by UV-B radiation on apple fruit surfaces. With the exception of lignin and folic acid, none of the compounds or mixtures increased significantly the ability of strain K to control the postharvest pathogen Penicillium expansum on wounded apple fruit. In contrast, casein, gelatine, tyrosine, congo red, riboflavin, and formulas 1 to 4 significantly reduced the effectiveness of strain K. Further investigations are justified to verify a potential benefit of lignin and folic acid for UV protection of strain K in preharvest applications.

Purification and characterization of mosquitocidal Bacillus sphaericus BinA protein

Certain strains of Bacillus sphaericus produce a highly toxic mosquito-larvicidal binary toxin during sporulation. The binary toxin is composed of toxic BinA (41.9kDa) and receptor binding BinB (51.4kDa) polypeptides and is active against vectors of filariasis, encephalitis and malaria. The toxin has been tested with limited use for the control of vector mosquitoes for more than two decades. The binA gene from a local ISPC-8 strain of B. sphaericus that is highly toxic to Culex and Anopheles mosquito species was cloned into pET16b and expressed in Escherichia coli. The purified BinA protein differs by one amino acid (R197M) from BinA of the highest toxicity strains 1593/2362/C3-41. Majority of the expressed protein was observed in inclusion bodies. BinA inclusions alone from E. coli did not show toxic activity, like reported previously. However, the active form of BinA could be purified to homogeneity from the soluble fraction of E. coli cell lysate, grown at reduced temperature after isopropyl beta-d-thiogalactopyranoside induction. The purified BinA protein with and without poly-histidine tag showed LC(50) dose of 82.3 and 66.9ngml(-1), respectively, at 48h against Culex quinquefasciatus larvae. The secondary structure of BinA is expected to be mainly beta strands as estimated using far-UV circular dichroism. The estimates matched well with the secondary structure predictions using amino acid sequence. This is the first report of large-scale purification and accurate toxicity estimation of soluble B. sphaericus BinA. This can help in design and synthesis of improved bacterial insecticide.