Poly(3-hydroxybutyrate) biosynthesis in the biofilm of Alcaligenes eutrophus, using glucose enzymatically released from pulp fiber sludge

Glucose, enzymatically released from pulp fiber sludge, was combined with inorganic salts and used as a growth medium for Alcaligenes eutrophus, a gram-negative strain producing poly(3-hydroxybutyrate) (PHB). By controlling the concentrations of the inorganic salts in the growth medium, almost 78% of the cell mass was converted to pure PHB. Efforts were made to find conditions for bacterial growth in the form of a biofilm on a cheap and reusable carrier. A number of positively charged carriers were tested, and the anion exchanger DEAE-Sephadex A-25 was chosen as a microcarrier for packed-bed biofilm cultures of A. eutrophus. Conditions for attachment, growth, and detachment were established. Biofilm formation on the microcarrier is strongly dependent on the ionic strength of the attachment medium. In order to achieve formation of the biofilm and its recovery from the microcarrier, the ionic strengths of the attachment and the detachment media were varied. Low ionic strength was tested for attachment, and high ionic strength was tested for detachment. Although biofilm formation in the packed-bed reactor is limited, the volumetric yield of cells based on the void volume of the packed bed is comparable with the batch culture yield.