The surroundings of livestock farms, including dairy farms, are known to be a major source of development and transmission of antibiotic-resistant bacteria. To control antibioticresistant bacteria in the livestock breeding environment, farms have installed livestock wastewater treatment facilities to treat wastewater before discharging the final effluent in nearby rivers or streams. These facilities have been known to serve as hotspots for inter-bacterial antibiotic-resistance gene transfer and extensively antibiotic-resistant bacteria, owing to the accumulation of various antibiotic-resistant bacteria from the livestock breeding environment. This review discusses antibiotic usage in livestock farming, including dairy farms, livestock wastewater treatment plants as hotspots for antibiotic resistant bacteria, and nonenteric gram-negative bacteria from wastewater treatment plants, and previous findings in literature.

Enterobacter sakazakii (Cronobacter spp.) causes meningitis, necrotizing enterocolitis, sepsis, and bacteremia in neonates and children and has a high mortality rate. For rapid E. sakazakii detection, various differential and selective media containing α-glucosidase substrates, such as 5-bromo-4-chloro-3-indolyl-α-D-glucopyranoside (BCIG) or 4-methylumbelliferyl-α-D-glucoside (α-MUG), have been developed as only E. sakazakii exhibits α-glucosidase activity in the genus Enterobacter. However, Escherichia vulneris (family: Enterobacteriaceae) can also utilize α-glucosidase substrates, thereby resulting in false positives. Various iron sources are known to promote the growth of gram-negative bacteria. This study aimed to develop a selective medium containing α-glucosidase substrates for E. sakazakii detection that would eliminate false positives, such as those of E. vulneris, and to determine the role of iron source in the medium. Three previously developed (TPD) media, i.e., Oxoid, OK, and VRBG, and the medium developed in this study, i.e., NGTE, were evaluated using 58 E. sakazakii and 5 non-E. sakazakii strains. Fifty-four E. sakazakii strains appeared as fluorescent or chromogenic colonies on all four media that were assessed. Two strains showed colonies on NGTE medium and not on TPD media. In contrast, the remaining two strains showed colonies on TPD media and not on NGTE medium. None of the non-E. sakazakii strains showed fluorescent or chromogenic colonies on any of the evaluated media except E. vulneris, which showed colonies on TPD media and not on NGTE medium. This study demonstrated that the newly developed NGTE medium was not only equally efficient in promoting the growth of bacterial colonies when compared with the currently available media but also eliminated false positives, such as E. vulneris.

Lactase (β-galactosidase) is abundant in the small intestine during early childhood and gradually decreases with age. Lactic acid bacteria (LAB) present in yogurt could survive in the stomach, and lactase produced by these LAB can aid in lactose breakdown in the small intestine, thereby reducing lactose intolerance. This study aims to provide preliminary data for development of lactose-free yogurts for the elderly, and investigate the effect of lactose-hydrolyzed milk on the growth of starter cultures. The pH during yogurt fermentation using lactose-free milk was slightly higher at 2 and 4 h of incubation, but reached 4.5 at the end of incubation, similar to that of the yogurt prepared from regular milk. The number of viable cells of Streptococcus thermophilus reached 108 CFU/mL after 2 h of incubation and increased to 109 CFU/mL after 4 h of incubation. During yogurt fermentation, the viable cells of Lactobacillus species and Bifidobacterium longum did not affect lactose hydrolysis. Although lactose-hydrolyzed milk did not promote the growth of starter cultures, manufacturing yogurt with lactose-free milk could be beneficial for the intestinal health of lactose-sensitive elderly.

본 연구에서는 CPP와 CSO를 사용하여 제조한 나노 복합체의 유식품 적용성 및 포집된 생리활성물질인 비타민 D의 in vitro release를 평가하였다. 그 결과, CPP/CSO 나노 복합체는 model milk 및 model yogurt 적용 후 12일간의 저장기간 동안 높은 물리적 안정성을 지녀 식품 적용성이 뛰어남을 규명하였다. 또한 제조 공정 요인인 CPP 농도와 pH 조절을 통해 비타민 D를 90% 이상 포집할 수 있었으며, in vitro release 평가를 통해 비타민 D를 위에서 보호하고, 장에서 release 하는 나노 복합체의 특성을 규명하였다. 결론적으로 본 연구에서 제조된 CPP/CSO 나노 복합체는 뛰어난 유식품 적용성을 지닐 뿐만 아니라, 칼슘흡수 증진을 위한 비타민 D를 효과적으로 포집할 수 있으며, 포집된 비타민 D를 소장까지 안전하게 전달할 수 있는 효과적인 나노 전달체로 활용될 수 있을 것으로 기대된다.

This study aimed to evaluate the biological potential of functional food, i.e., specific peptides obtained from the hydrolysis of milk protein, by assessing their antioxidant and antibacterial properties. For the preparation of casein hydrolysates, commercial enzymes were added to 10% casein solution in a 1:200 (w/v) ratio, and samples were collected each hour. Based on the assessment of the degree of hydrolysis (DH) of casein hydrolysates, it was observed that the concentration of all enzymatic hydrolysates increased rapidly from 30 to 40 minutes. However, no change was observed in their concentrations after 150 minutes. Protamex® and Neutrase® exhibited the highest DH when compared to other enzymes. Furthermore, SDS-PAGE was performed for analyzing the proteolytic pattern of each enzyme, except for Flavourzyme®, and peptides in the size range of 20-25 kDa were identified. Subsequently, peptides produced by two enzymes were isolated using a preparative liquid chromatography system. Overall, NF3, NF4, PF5, and PF6 showed higher antioxidant potential than other peptide fractions. Moreover, NF7 and PF3 exhibited the highest antibacterial activity. In this study, we evaluated the biological potential of novel casein-derived peptides that may find application in the food and healthcare industry.