Comparative characterization and identification of bioactive peptides in protein hydrolysates from edible insects

다국어 초록 (Multilingual Abstract)

Edible insects have been attracting attention as an alternative protein source. So, at present a comprehensive study of insect proteins is greatly needed. The objective of our study was to deliver an inclusive investigation of protein hydrolysates from seven species of edible insects through a determination of their physicochemical and physiological properties obtained after partial purification and identification of active fractions. Proteins were extracted from defatted samples, and then treated with commercial proteases including flavourzyme, alcalase and a mixture of both. The physicochemical properties of the hydrolysates, including solubility and emulsifying properties generally increased as compared to the control. For the hydrolysate of crickets, it was determined that alcalase was the proper emulsifying agents to employ due to its high stability. As results of evaluating foaming properties, the protein solution of silkworm pupae recorded the highest protein level, being comparable to sodium caseinate. With regards α-glucosidase inhibitory effects, bombyx batryticatus was found to be the most effective. Anti-inflammatory activity was only found in silkworm pupae and bombyx batryticatus, but this decreased as it underwent hydrolysis. Significant increases were observed in ACE inhibition with hydrolysis, especially in the case of the alcalase treated hydrolysates from crickets. Therefore, its hydrolysate was selected for partial purification using preparative HPLC with the alcalase treated hydrolysate from silkworm pupae, which showed the highest yield. As a result of purification, silkworm pupae 3-2b.b and crickets 4-3a fractions, which recorded the highest activities, were selected, and then identified by MALDI-TOF/TOF. Silkworm pupae 3-2b.b was identified as having DRF, DGRL, ATYK and LRW peptides. In addition, CF and DWM peptides were found in crickets 4-3a. These results presented the functional properties of protein and hydrolysates from edible insects that may be potentially useful in the food and functional food industry in the future.

국문 초록 (Abstract)

식용 곤충은 기존 단백질의 대체 자원으로 주목받고 있다. 따라서, 곤충 단백질에 대한 추가 연구가 필요한 시점이다. 본 연구의 목적은 식용 곤충 7종의 단백질 가수분해물의 물리적 특성 및 생리활성 특성을 규명 및 비교하고 활성 분획물을 분리 및 정제 후 규명하는 것이다. 탈지 시료로부터 단백질을 추출한 후 상업 효소인 flavourzyme, alcalase와 두 효소의 mixture를 처리하여 가수분해물을 제조해 실험이 이용하였다. 물리적 특성에서 용해도와 유화특성은 전체적으로 효소처리 시 수치가 증가하였다. 귀뚜라미 alcalase 분해물은 높은 안정성으로 적절한 유화제로 결정되었다. 기포 특성 측정 결과, 번데기 단백질용액이 가장 우수했고 이 수치는 기존에 사용되는 카세인 나트륨에 필적하였다. α-glucosidase 저해능 측정 결과, 백강잠이 가장 효과적이었으며 항염증 활성 측정 결과, 번데기와 백강잠에서 활성이 측정되었지만 가수분해 시 활성이 감소하였다. Angiotensin-I 전환효소(ACE) 저해능은 가수분해 시 유의적으로 증가하였고, 특히 귀뚜라미 alcalase 분해물이 가장 우수하였다. 이 분해물과 수율이 가장 좋았던 번데기 alcalase 분해물을 분취용 HPLC로 분리 및 정제하였다. 이 결과, 가장 활성이 좋은 번데기 3-2b.b, 귀뚜라미 4-3a 정제물을 얻었고, MALDI-TOF/TOF로 분석하였다. 분석 결과, 번데기 정제물에서는 DRF, DGRL, ATYK, LRW가, 귀뚜라미에서는 CF, DWM이 구성 펩타이드로 규명되었다. 이 결과는 식용 곤충 유래 단백질과 가수분해물의 기능 특성이 미래 식품 및 건강기능식품 시장에서 이용될 가능성이 충분하다는 것을 보여준다.

목차 (Table of Contents)

• I. Introduction 1
• II. Materials and Methods 6
• 1. General materials 6
• 2. Lipid removal and protein extraction 6
• 3. Preparing hydrolysates 7
• 4. Physicochemical properties 8
• 5. Physiological properties 10
• 6. Partial purification 14
• 7. Identification 17
• 8. Statistical analysis 18
• III. Results and Discussion 19
• 1. Yield of proteins (%) 19
• 2. Physicochemical properties 20
• 3. Physiological properties 32
• 4. Partial purification 43
• 5. Identification 57
• IV. Conclusion 61
• V. References 63
• 국문초록 73