Da. Rickert et al., IMPROVED ORGANIC-ACID PRODUCTION BY CALCIUM ALGINATE-IMMOBILIZED PROPIONIBACTERIA, Enzyme and microbial technology, 22(5), 1998, pp. 409-414
Propionic and acetic acid production by Propionibacterium cells immobi
lized in calcium alginate beads was evaluated in 12-h repeated-batch f
ermentations on glucose and lactate as primary carbon sources. Beads c
ontained approximately 2 x 10(11) cells g(-1) (wet weight) and were ad
ded at 40% of broth volume. High initial substrate concentrations (up
to 115 gl(-1) glucose and up to 78 gl(-1) lactate) were utilized by th
e immobilized cells. The best substrate utilization rates and acid yie
lds were obtained al 75 gl(-1) initial glucose and 42 gl(-1) initial l
actate; 34 gl(-1) and 22 gl(-1) propionate were produced respectively,
at these substrate concentrations in 12 h. The ratio of propionic to
acetic acid increased to 9:1 with increasing glucose concentration, bu
r remained at 2:1 at the different initial lactate concentrations test
ed. Glucose consumption and propionate production rates were higher in
fermentations controlled at pH 6.0 than at pH 7.0, but yields of acid
s from glucose were highest at pH 7.0. (C) 1998 Elsevier Science Inc.