갈색거저리 유충의 사료인 밀기울은 대부분 수입에 의존하고 있는데 일부 국가의 식량 수출 중단 조치 등에 따른 국제 곡물가격 상승으로 밀기울 가격은 인상되고, 식용곤충 판매가격이 하락하면서 생산비 절감을 위한 사료 개발이 요구되고 있다. 농업부산물 3종을 50% 이상 급이하게 되면 유충 생육이 저하되었기 때문에 본 연구는 적정한 배합비율을 선정하기 위해 첨가사료 20, 30% 함량으로 밀기울과 혼합하여 사료를 급이하였을 때 갈색거 저리 유충의 생육 특성과 영양성분 변화에 대해 밀기울만 제공한 대조구와 비교하였다. 부산물 A와 B, C를 각각 30% 함유한 처리구에서 갈색거저리 유충 무게는 대조구와 차이가 없음을 확인하였다. 먹이소화율은 부산물B를 20% 함유한 처리구가 80.5%로 대조구에 비해 높았고, 부산물C 30% 처리구에서 72.6%로 가장 낮았다. 갈색거저 리 유충의 생육일수 100일 기준으로 부산물B 30% 처리구에서 용화율이 76.1%로 대조구보다 1.6배 높았으며, 부산물A 20% 처리구는 29.2%로 용화율이 가장 낮았다. 갈색거저리 유충의 조단백질 함량은 부산물 C 30% 처리 구에서 대조구보다 10.3% 증가하여 아미노산 분석을 진행한 결과 sarcosine과 ornithine이 2.5배 이상 증가하였다. 이를 통해 부산물 B나 C를 30% 함유한 사료를 급이하였을 때 사육 원가를 절감하여 유충을 생산할 수 있을 것으로 사료된다.

Antimicrobial peptides (AMPs) can be produced in mealworms. In this work, we integrated Bombyx mori (Bm) AMP, cecropin A to Beauveria bassiana ERL1170 by restriction enzyme-mediated integration method, which was confirmed by RT-PCR and an antibacterial activity assay. For the extracellular secretion of Bm cecropin A protein, the active domain of the cecropin A gene was tailed to the signal sequence of B. bassiana chitinase (Bbs). To exchange Bbs-cecropin A gene with egfp gene in pBARKS1-egfp, Bbs-cecropin A fragment was cut from pGEMBbs-cecropin A using XbaI/blunted and BamHI and ligated with cut pBARKS1-egfp using NcoI/blunted and BamHI, designated as pBARKS1-Bbs-cecropin A. After the transformation, transformants were grown on Czapek’s solution agar containing 600 μg ml-1PPT. Expression of Bm cecropin A was confirmed by RT-PCR. Strong clear zone was observed in the co-culture of the transformant D-6 and Bacillus subtilis on fourth strength Sabouraud dextrose agar 1 day after the culture at 25°C, whereas the wild type had no clear zone. This work suggests that Bm cecropin A can be efficiently produced in this mealworm-based fungal expression platform, thereby increasing the value of mealworms in the animal feed additive industry.

Antimicrobial peptides (AMPs) can be produced in mealworms, currently being used as animal feeds, by the infection of genetically engineered-entomopathogenic fungi. In this work, we integrated Bombyx mori (Bm) AMP, cecropin A to Beauveria bassiana ERL1170 by restriction enzyme-mediated integration method, which was confirmed by RT-PCR and an antibacterial activity assay. For the extracellular secretion of Bm cecropin A protein, the active domain of the cecropin A gene was tailed to the signal sequence of B. bassiana chitinase (Bbs). To exchange Bbs-cecropin A gene with egfp gene in pBARKS1-egfp, Bbs-cecropin A fragment was cut from pGEM-Bbs-cecropin A using XbaI/blunted and BamHI and ligated with cut pBARKS1-egfp using NcoI/blunted and BamHI, designated as pBARKS1-Bbscecropin A. After the transformation, transformants were grown on Czapek’s solution agar containing 600 μg ml-1PPT. Expression of Bm cecropin A was confirmed by RT-PCR. Strong clear zone was observed in the co-culture of the transformant D-6 and Bacillus subtilis on fourth strength Sabouraud dextrose agar 1 day after the culture at 25°C, whereas the wild type had no clear zone. This work suggests that Bm cecropin A can be efficiently produced in this mealworm-based fungal expression platform, thereby increasing the value of mealworms in the animal feed additive industry.

As a part of a study on insect food, the nutritional and harmful components in the mealworm (Tenebrio molitor) were analyzed. In addition, due to a recent introduction of live Chinese mealworm in the Korea market, those components between the Korean and Chinese mealworms were compared. Analysis of the composition of the general components (moisture, crude protein, crude fat, crude ash, crude fiber, and carbohydrates) showed that abundant crude protein (50.32– 52.79%) was present in both Korean and Chinese mealworm powders, and the protein content in the Chinese mealworm powder was higher than that in the Korean mealworm powder by 2.67%. The amino acid compositions were similar, but the fatty acid composition differed with respect to each component in the Korean and Chinese mealworm powders. The unsaturated fatty acid contents were 76.80-80.55% of the total fatty acid content in the mealworms. The linoleic acid contents in the Korean and Chinese mealworms were 20.8±1.1% and 34.69±1.9%; the linolenic acid contents, 0.47% and 1.31%; and the oleic acid contents, 51.40±0.9% and 40.20±1.5%, respectively. With respect to harmful components such as heavy metals and bacteria that cause food poisoning, bacteria such as Escherichia coli O157:H7 and Salmonella spp. were not detected in both Korean and Chinese mealworms, and the mercury content was below the standard value for common food (Korea, 0.03 mg/kg; China, 0.08 mg/kg).

Mealworms, Tenebrio molitor (L.) is used as an important animal feed additive for growth promotion and health management, but potentially exposes to fungal infection. In this work, virulence of two species of entomopathogenic fungi against the insect, and the relationship between abiotic features and virulence were investigated. Secondly our consideration was also given to the effect of chemical fungicides on conidial germination for risk control. Between Beauveria bassiana (Bb) and Metarhizium roberstii (Mr) (previously M. anisopliae), Bb isolates had much higher virulence (~100% mortality in 3~4 days after the treatment), rather than Mr isolates in laboratory assays. Next, fungus-treated mealworms were kept at wheat bran at 20, 25, 30 and 35℃ with 3, 6, 9 times of water spray to the feeds for set-up of different humidity conditions. Inoculation of fungi to mealworms was conducted by fungal spray and feeding methods, which resulted in higher virulence in feeding method. In the feeding method, all temperature treatments except 35℃ showed high virulence against mealworms, but any significant relationship between virulence and humidity was not observed. In the chemical fungicide screening, fluazinam (CAS No. 79622-59-6) and mancozeb (8018-01-7) significantly inhibited the germination of Bb and Mr conidia. This work suggest that contamination of wheat bran with fungal pathogens, particularly B. bassiana may induce mycosis of mealworms, but introduction of effective fungicides possibly reduce fungal infection.