Growth Profiles and Temporal Accumulation of Aniline-Blue-Reactive β-(1→3)-Glucan-Associated Material in Alcaligenes faecalis A12C Batch Cultures

Microbial exopolysaccharides (EPSs) are functional biopolymers of growing scientific and industrial interest because of their structural diversity, biocompatibility, and rheological properties. Microbial β-(1→3)-glucans are of particular biological and technological interest, and their production depends strongly on strain characteristics, medium composition, and culture conditions. This study characterized the temporal relationship among bacterial growth, viability, and aniline-blue reactivity in Alcaligenes faecalis A12C under batch growth and fermentation conditions. Growth turbidity, viable bacterial concentration, and β-(1→3)-glucan-associated signals were monitored over 96 h using spectrophotometric, microbiological, and microscopic approaches. In growth culture medium (GCM), OD600 increased after 24–30 h and reached approximately 2.4 at 72 h, coinciding with the highest viable count (2.44 × 1021 CFU/mL). Aniline-blue coloration became clearly detectable after 30 h and persisted through 96 h, when microscopy showed blue staining associated with bacterial cells. In fermentation culture medium (FCM), OD600 increased progressively to approximately 2.8 at 96 h, whereas viable counts followed a distinct temporal profile. Aniline-blue reactivity changed during the first 24 h and remained close to an A610 of approximately 1.0 thereafter. These findings indicate distinct temporal patterns among culture turbidity, viability, and aniline-blue reactivity and provide a framework for subsequent structural characterization of the detected material.