title: New Tween-80 microbiological assay of serum folate levels in humans and animals.
abstract: The objective of this study was to develop a new Tween-80 microbiological assay (Tween-80 MBA) to determine human or animal serum folate levels and to verify its reliability. The effects of the Lactobacillius casei subspecies rhamnosus (L. casei, ATCC No. 7469) inoculum concentration, incubation time, and Tween-80 on L. casei growth were studied, and the serum folate levels were investigated. Serum samples were collected from patients with esophageal cancer (EC) and healthy control subjects in Yanting, healthy adult subjects in Chengdu, Sichuan, and in male Sprague-Dawley rats. Optimal conditions for the new MBA were as follows: 1.28 x 10(7) CFU/mL working inoculum, vitamin folic acid assay broth with 0.24% (w/w) Tween-80, and anaerobic incubation with L. casei at 37 degrees C for 22 h. Under the optimal conditions, the working curve was in simple linear rather than logarithmic equation; the linear working curve of the folic acid standard working solution concentration versus the turbidity (adsorption value) of medium with L. casei ranged from 0.05 to 1.00 microg/L; the linear correlation coefficient was 0.9989 (SD 0.0007); the recovery rate of folate was 105.4-112.7%; and the minimum concentration for detecting folate was 0.03 microg/L. The RSD within-day and between-day precisions were 5.6 and 3.3%, respectively. The serum folate level of 100 EC patients was 6.4 (SEM 0.4) microg/L which was significantly lower than that of healthy control subjects [8.0 (SEM 0.6) microg/L, n = 100, P=0.020]. The new Tween-80 MBA is considered to be a reliable method for measuring serum folate level.
authors.affiliation: Sichuan University, West China School of Public Health, Department of Nutrition and Food Hygiene, Chengdu 610041, People's Republic of China.
authors.forename: Zhenghua
authors.initials: Z
authors.lastname: Zhou
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yang
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Chong
authors.initials: C
authors.lastname: Kou
authors.forename: Ping
authors.initials: P
authors.lastname: Xiao
authors.forename: Yan
authors.initials: Y
authors.lastname: Jiang
authors.forename: Junrong
authors.initials: J
authors.lastname: Hong
authors.forename: Chengyu
authors.initials: C
authors.lastname: Huang
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D001681:Biological Assay / Q000379:methods* / Q000592:standards; D005260:Female; D005492:Folic Acid / Q000097:blood*; D006801:Humans; D007780:Lacticaseibacillus casei / Q000378:metabolism; D052201:Lacticaseibacillus rhamnosus / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011136:Polysorbates / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D055815:Young Adult
chemical_list: D011136:Polysorbates; D005492:Folic Acid