Transformation of food waste to source of antimicrobial proteins by black soldier fly larvae for defense against marine Vibrio parahaemolyticus

Principle Investigation and Method Standardization of Inhibition Zone Assay Based on Antimicrobial Peptides Extracted from Black Soldier Fly Larvae

The black soldier fly is a valuable resource insect capable of transforming organic waste while producing antimicrobial peptides (AMPs). The inhibition zone assay (IZA) is a method used to demonstrate the antimicrobial activity of AMPs. This study aimed to examine the experimental principles and establish a standardized IZA method. Results indicated that the AMPs extract consisted of proteins ranging in molecular weights from 0 to 40 kDa. The AMPs diffused radially on an agar plate through an Oxford cup. The diffusion radius was influenced by the concentration and volume of the AMPs but ultimately determined by the mass of the AMPs. The swabbing method was found to be effective for inoculating bacteria on the agar plate. Among the conditions tested, the plate nutrient concentration was the most sensitive factor for the IZA, followed by bacterial concentration and incubation time. Optimal conditions for the IZA included a nutrient plate of 0.5× TSA, a bacterial concentration of 106 CFU/mL, and an incubation time of 12 h, with oxytetracycline (OTC) at 0.01 mg/mL serving as the positive control. The antimicrobial-specific activity of AMPs could be standardized by the ratio of inhibition zone diameters between AMPs and OTC. These findings contribute to the standardization of the IZA method for profiling the antimicrobial activity of AMPs.

Molecular Characterization of the Allergenic Arginine Kinase from the Edible Insect Hermetia illucens (Black Soldier Fly)

SCOPE

Arginine kinase (AK) is an important enzyme for energy metabolism of invertebrate cells by participating in the maintenance of constant levels of ATP. However, AK is also recognized as a major allergen in insects and crustaceans capable of cross-reactivity with sera of patients sensitized to orthologous proteins. In the perspective of introducing insects or their derivatives in the human diet in Western world, it is of primary importance to evaluate possible risks for allergic consumers.

METHODS AND RESULTS

This work reports the identification and characterization of AK from Hermetia illucens commonly known as the black soldier fly, a promising insect for human consumption. To evaluate allergenicity of AK from H. illucens, putative linear and conformational epitopes are identified by bioinformatics analyses, and Dot-Blot assays are carried out by using sera of patients allergic to shrimp or mites to validate the cross-reactivity. Gastrointestinal digestion reduces significantly the linear epitopes resulting in lower allergenicity, while the secondary structure is altered at increasing temperatures supporting the possible loss or reduction of conformational epitopes.

CONCLUSION

The results indicate that the possible allergenicity of AK should be taken in consideration when dealing with novel foods containing H. illucens or its derivatives.

Effects of partial or complete replacement of soybean meal with commercial black soldier fly larvae (Hermetia illucens) meal on growth performance, cecal short chain fatty acids, and excreta metabolome of broiler chickens

Black soldier fly larvae meal (BSFLM) is receiving great attention as a rich source of protein and antimicrobials for poultry. Therefore, we evaluated the effects of partially or completely replacing soybean meal (SBM) with commercial BSFLM on growth performance, tibia traits, cecal short chain fatty acid (SCFA) concentrations, and excreta metabolomes in broiler chickens (Gallus gallus domesticus). A total of 480 day-old male Ross × Ross 708 chicks were assigned to 6 diets (8 replicates/diet): a basal corn-SBM diet with in-feed bacitracin methylene disalicylate (BMD), a corn-SBM diet without BMD (0% BSFLM), and four diets in which the SBM was substituted with 12.5, 25, 50, and 100% BSFLM. Body weight (BW), feed intake (FI) and cumulative feed conversion ratio (cFCR) were monitored on days 14, 28, and 35. Cecal SCFA levels were determined on days 14, 28, and 35. Tibia traits and excreta metabolomes were determined on day (d) 35. On d14, birds fed 12.5 and 25% BSFLM had a similar BW, FI, and cFCR as birds fed BMD (P > 0.05). On d 35, birds fed 12.5% BSFLM had a similar BW, FI and cFCR as birds fed BMD or 0% BSFLM (P > 0.05). For each phase, birds fed 100% BSFLM had a lower BW, FI and higher cFCR than birds fed BMD or 0% BSFLM (P < 0.05). On d 35, BW decreased linearly, quadratically, and cubically with increasing levels of BSFLM (P < 0.01). Overall (d 0-35), BSFLM linearly, quadratically, and cubically decreased FI and quadratically and cubically increased cFCR (P < 0.01). Quadratic responses were observed for tibia fresh weight (P = 0.049) and ash content (P = 0.022). BSFLM did not impact cecal SCFAs levels. The excreta metabolome of birds fed 100% BSFLM clustered independently from all other groups and exhibited greater levels of putatively identified methionine, lysine, valine, glutamine, histidine and lower levels of arginine as compared to all diets. Taken together, substitution of SBM with ≤25% of BSFLM in the starter phase may be used as an alternative to BMD.

From Medical Herb to Functional Food: Development of a Fermented Milk Containing Silybin and Protein from Milk Thistle

Milk thistle is a traditional medicinal herb. Silybin is a medicinal component found in the seed coat of milk thistle, which has liver-protective and anti-cancer properties. Conventional studies have focused on the extraction of silybin with organic reagents, which was inapplicable to the food industry. This study aims to develop a fermented milk containing silybin and protein from the milk thistle seeds. A three step procedure was developed, comprising homogenization of milk thistle seeds, NaHCO₃ heat treatment, and microbial fermentation. The silybin was characterized by high performance liquid chromatography, and the protein was quantified and electrophorized. It was found that the homogenization step was essential for the preparation of protein, and the NaHCO₃ heat treatment was the crucial step in obtaining silybin. The optimal NaHCO₃ treatment settings were 1% NaHCO₃, 60°C, and 3 h, and the optimal strains for microbial fermentation were L131 (Rummeliibacillus stabekisii) and RS72 (Lactobacillus plantarum). The silybin yield in the fermented milk reached 11.24-12.14 mg/g seeds, accounting for 72.6-78.4% of the total silybin in the milk thistle seeds, and the protein yield reached 121.8-129.6 mg/g seeds. The fermented milk had a slightly sweet yoghurt-like flavor and could be used as a dietary supplement for silybin and protein.