Exposure assessment of benzoic acid from processed foods in South Korea.

To evaluate the dietary exposure to benzoic acid of Korean consumers, the daily intake of benzoic acid was estimated using benzoic acid concentrations from processed food survey data in South Korea and food consumption data from the Korean National Health and Nutrition Examination Survey in 2018. The results were compared with the acceptable daily intake (ADI) stipulated by the Joint FAO/WHO Expert Committee on Food Additives. In addition, we estimated the effects and risk of benzoic acid intake, which may be increased by including amounts of naturally occurring benzoic acid recently established by the Ministry of Food and Drug Safety. Benzoic acid analyses were conducted in South Korea in 2020 for a total of 127,628 samples; it was detected in 1,803 samples, a detection rate of 1.4%. The mean contents of total samples and detected samples were 1.3 mg/kg and 89.4 mg/kg, respectively. The estimated daily intake (EDI) of benzoic acid for average consumers using a mean value of detected samples was 207.3 µg/kg.bw/day, which is 4.1% of ADI. The EDI of benzoic acid for high consumers (95th percentile) of processed foods among the consumers was 1,406.7 µg/kg.bw/day, which is 28.1% of the ADI. As a result of estimating the intake of benzoic acid, which may be increased by a newly established standard on natural occurrence in South Korea, the theoretical maximum EDI of benzoic acid was 109.9 µg/kg.bw/day, which is 2.2% of the ADI.

Cerulenin-mediated apoptosis is involved in adenine metabolic pathway.

Cerulenin, a fatty acid synthase (FAS) inhibitor, induces apoptosis of variety of tumor cells. To elucidate mode of action by cerulenin, we employed the proteomics approach using Schizosaccharomyces pombe. The differential protein expression profile of S. pombe revealed that cerulenin modulated the expressions of proteins involved in stresses and metabolism, including both ade10 and adk1 proteins. The nutrient supplementation assay demonstrated that cerulenin affected enzymatic steps transferring a phosphoribosyl group. This result suggests that cerulenin accumulates AMP and p-ribosyl-s-amino-imidazole carboxamide (AICAR) and reduces other necessary nucleotides, which induces feedback inhibition of enzymes and the transcriptional regulation of related genes in de novo and salvage adenine metabolic pathway. Furthermore, the deregulation of adenine nucleotide synthesis may interfere ribonucleotide reductase and cause defects in cell cycle progression and chromosome segregation. In conclusion, cerulenin induces apoptosis through deregulation of adenine nucleotide biosynthesis resulting in nuclear division defects in S. pombe.

The first two-dimensional reference map of the fission yeast, Schizosaccharomyces pombe proteins.

Cytosolic proteins of Schizosaccharomyces pombe were separated by two-dimensional (2-D) gel electrophoresis, to construct the first 2-D reference map. In the pI range 4-7, more than 500 spots were detected by silver staining, and 70 different proteins corresponding to 111 spots were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry and tandem mass spectrometry, where necessary. In the pI range 6-9, approximately 330 spots were detected, and 31 proteins corresponding to 38 spots were identified by mass spectrometry. More than 50% of the identified proteins were involved in amino acid, carbohydrate or nucleotide metabolism, and energy production. A second large group of identified proteins comprises heat shock and other stress related proteins and chaperones.

Characterization of a carotenoid-hyperproducing yeast mutant isolated by low-dose gamma irradiation.

To isolate a carotenoid-hyperproducing yeast, Phaffia rhodozyma was treated by low-dose gamma irradiation below 10 kGy. Through repeated rounds of gamma irradiation and visual screening, a mutant 3A4-8 was isolated. It produced 3.3 mg of carotenoid per gram of yeast, 50% higher carotenoid content than that of the unirradiated strain. Glucose and peptone were the most suitable carbon and nitrogen sources for production of carotenoid based on the growth experiment of the mutant under various carbon and nitrogen sources. This result suggests that low-dose gamma irradiation could be used as a means of mutagenesis for isolation of a carotenoid-hyperproducing strain of P. rhodozyma because only the carotenoid-hyperproducing yeast survives gamma irradiation by scavenging oxygen radicals generated by radiolysis of water.