N. A. Ushakova

Paramagnetics melanin and Mn2+ in black soldier fly Hermetia illucens

Larva, prepupa (last instar larva), pupa, and an empty shell of pupa after hatching of the black soldier fly Hermetia illucens contain eumelanin, an active synthesis of which is observed at the prepupal stage, which is probably due to the release of prepupa from the feed substrate thickness to the open space for pupation. It was shown for the first time that prepupa contains high quantities of the magnetically active form of manganese Mn2+. This fact indicates that Mn2+ stimulates the copper-containing tyrosinase—the key enzyme in the synthesis of melanin in the period of migration and adaptation of the insect to the solar radiation.

Mechanisms of the Effects of Probiotics on Symbiotic Digestion

The published data and our own data on the mechanisms of the influence of microbial probiotics, prebiotics, and their combinations on the processes of symbiotic digestion have been considered and generalized. It is shown that the effects on an organism are associated with the enhanced metabolic activity of intestinal bacteria: stimulation of bacterial fermentation of carbohydrates and formation of short-chained fatty acids, an increase in the blotting capacity of the intestines due to elongation of villi and deepening of crypts, and a decrease in secretion of toxic proteolytic products (ammonia, phenols, thiols, indoles, etc.). It has been shown that a combination of probiotics and prebiotics enhances the biological efficiency of a complex preparation, which contributes to activation of carbohydrate, protein, and mineral metabolism.

Features of the effect of a complex probiotic with Bacillus bacteria and the larvae of Hermetia illucens biomass on Mozambique tilapia (Oreochromis mossambicus × O. niloticus) and Russian sturgeon (Acipenser gueldenstaedti) fry

A study of the effect of a complex probiotic preparation with bacteria of the genus Bacillus and a microdose of larvae of the fly Hermetia illucens on the physiological parameters of fish has been carried out. It was established that introduction of the complex into artificial feeds for tilapia and Russian sturgeon juveniles during their incubation in recirculating aquaculture systems improves the digestion efficiency and increases the rate of fish growth and body mass accumulation. In tilapia, a decrease in the cholesterol level was revealed, while in sturgeon, an increase in the hemoglobin content was found. It was noted that a probiotic with biologically active agents H. illucens had a stimulating effect on the development of sexual gonads in female sturgeon fry, promoted an increase in the ovary mass, and provided for the development of eggs without morphological disturbances.

Special effects of a complex probiotic containing cellulolytic bacteria Cellulomonas on actively growing rabbits

It was shown that the association of probiotic bacteria of the genuses Bacillus and Cellulomonas form biolayers on the surface of beet marc particles. The positive effect of a fodder additive that contained the biolayer on the basis of a phytomatrix on the growth and development of young rabbits was shown. Feeding of animals with a mixed fodder that contained 0.1% preparation resulted in stimulation of digestion of all components of the food. Among other components of the mixed fodder, cellulose was digested most effectively. An increase in the biomass of symbiotic bacteria and enzymatic activity in the blindgut chymus was also observed. The positive nitrogen balance demonstrated an increase in the nitrogen content in animals and a decrease of its losses with excretion. The mechanism of response of the rabbit’s organism to introduction of the complex probiotic preparation into the digestive tract is discussed.

Nitrogen requirements of Microtus rossiaemeridionalis

Total nitrogen requirements in the small herbivorous rodent Microtus rossiaemeridionaliswere studied. When provided with two kinds of standard laboratory food (about 20% and 0% digestible protein, respectively) ad libitum(cafeteria diet), the voles chose a diet of 14% protein. The total daily (with urine and faeces) nitrogen losses were, in this case, determined as 3.65 ± 0. 60 mg N/ g of body mass. When provided with a protein-free diet alone, the animals lost 0.90 ± 0,05 mg N/ g body mass per day, comprising about 3% of their body mass daily. It was proposed that the consumption of a low-fiber diet (about 4% in both kinds of food) could affect the gastrointestinal bacterial flora and, thus, lead to changes in the primarily herbivorous nitrogen metabolism.

Melanin and Melanogenesis at Different Life Stages in Hermetia illucens

This work has demonstrated that the life stages of the Hermetia illucens fly are characterized by varying melanin contents with the maximum melanin amount being detected in the pupa. It has been observed that active synthesis of the pigment takes place in the prepupa and coincides with the time when the population migrated for pupation. It has been noted that a high manganese content in the prepupa and pupa indicates the important role that this biogenic element plays in organogenesis and melanogenesis in H. illucens. It has been revealed that in the imago and pupa, the melanin demonstrates broad-range antimicrobial activity and contribute to the insect protection against bacterial and fungal infections.

Biological Efficiency of the Prepupae Hermetia illucens in the Diet of the Young Mozambique Tilapia Oreochromis mossambicus

It has been noted that the introduction of small doses of dry prepupae of Hermetia illucens flies into the diet of the young Mozambique tilapia Oreochromis mossambicus (0.5 g/kg feed) had a positive effect on the growth and development of fish. It was found that the average daily gain in the experimental group was 0.7 g. It was established that the blood biochemical parameters were within the norm in the fish of all groups; however, in the experimental tilapia, the erythrocyte sedimentation rate was significantly lower and a tendency to increase in the amount of hemoglobin and glucose was noted. It was revealed that in the seminiferous tubules of fish in the experimental group, the number of mature sperm was 5.9 times higher compared with the control, indicating an increase in the rate of spermatogenesis. It is assumed that the observed effects are due to the high content of manganese in the prepupae present in a biologically active divalent form.

Preparation and Characterization of Alphitobius diaperinus Melanin

Melanin with a high antioxidant and sorption activity comparable to that of synthetic dioxyphenylalanine (DOPA)-melanin was isolated from the biomass of the darkling beetle Alphitobius diaperinus. The pigment was extracted with a solution of potassium hydroxide, followed by precipitation with concentrated hydrochloric acid and hydrolysis of the resulting precipitate with the same acid. The electron paramagnetic resonance (EPR) signal of melanin was characteristic of eumelanins with a spin concentration of 4.9 × 1017 spin per 1 g of dry weight. The melanin concentration that induced 50% inhibition of peroxidation was 9.2 μg/mL (the analogous concentration of DOPA-melanin was 8.0 μg/mL). The maximum of methylene-blue binding to the beetle melanin was 700 mg of dye per 1 g of dry weight of the preparation. The lipid-free melanin preparation exhibited antiradical activity.

Melanin properties at the different stages towards life cycle of the fly Hermetia illucens

Eumelanin type pigments are synthesized at all the stages of the life cycle of the fly Hermetia illucens: in the larvae, pre-pupae, pupae and adult flies (dead flies). The greatest content of melanin was recorded in the cuticles. Melanin was present not only in the cuticle, hence it remained in the cuticle after the emergence of the adult fly. It was also found in the insect body in a complex with lipids. In pupae, it is mostly lauric acid that was associated with melanin. Its proportion in the melanin-chitosan complex was 80%. The isolated melanin-chitosan complex of adult flies showed a wide range of antibacterial activity, inhibiting the growth of 21 out of the 25 of the test cultures. The melanin-chitosan complex of empty pupal membranes and alcohol suspension of pupal melanin inhibited twice as smaller number of test cultures and the above activity was absolutely in the pupal chitosan. The largest zone of growth inhibition was recorded with respect to Aspergillus niger, Candida albicans, salmonella, and Staphylococcus aureus. An alcohol suspension of pupal melanin inhibited the growth of 10 test cultures. In this case the greatest activity was shown in relation to Mycobacterium B5 and Acinetobacter sp. 1182.

Effect of Bacillus subtilis in feed probiotic on the digestion of fish cultured in cages

We studied the activity of the digestive enzymes, qualitative composition, and bacteria genera ratio in the intestinal chyme of carp Cyprinus carpio and sterlet Acipenser ruthenus grown on an artificial diet in cage culture. It was shown that the inclusion of live bacteria Bacillus subtilis in the probiotic ProStor had a positive impact on the size and the structure of the microbial community in intestinal chyme, on the activity of some digestive enzymes, and on the digestibility and the weight gain of carp and sterlet. The total amount of micro-organisms in the carp chyme was by 13% higher and in sterlet it was 3.5 times higher in the experimental groups compared to the control. In the studied species of fish, the increase in the activity of digestive enzymes was accompanied by the decrease in nitrogen, ammonia, and urea. Presumably, it happened because of better absorption of protein and more intensive use of nitrogen metabolites by intestinal microflora for the synthesis of their own biomass. The average daily weight gain of carp and sterlet was 25 and 35% higher, respectively, in the experimental groups than in the control.