FACTORS INFLUENCING THE SYNTHESIS OF POLYHYDROXYBUTYRATE DEPOLYMERASE IN STREPTOMYCES SP. 5A

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FACTORS INFLUENCING THE SYNTHESIS OF
POLYHYDROXYBUTYRATE DEPOLYMERASE IN STREPTOMYCES
SP. 5A
Matthew B. Persinger, Matthew Shull, and Stephen
F. Baron, Biology Dept., Bridgewater College,
Bridgewater, VA 22812
TABLE 1. EFFECT OF CARBON SOURCE ON PHB
DEPOLYMERASE SYNTHESIS
FIGURE 2. GLUCOSE REPRESSION OF PHB DEPOLYMERASE
SYNTHESIS
BACKGROUND
POLYHYDROXYBUTYRATE (PHB) IS ONE OF A GROUP OF
POLYMERS CALLED POLYHYDROXYALKANOATES (PHAs),
WHICH ARE PRODUCED BY VARIOUS SOIL BACTERIA.
THEY CAN BE USED AS PLASTIC SUBSTITUTES, BUT ARE
FULLY DEGRADABLE BY SOIL AND WATER BACTERIA. THE
ACTINOMYCETE, STREPTOMYCES SP. 5A, SECRETES A PHB
DEPOLYMERASE DURING GROWTH ON PHB. THIS ENZYME
DEGRADES PHB TO ITS MONOMERIC FORM,
3-HYDROXYBUTYRATE (3HB), WHICH IS THEN
METABOLIZED. THE HYDROLYSIS OF PHB PRODUCES
CLEARING ZONES IN AGAR MEDIA (FIG. 1). OUR
RESEARCH GOAL WAS TO IDENTIFY FACTORS THAT
REGULATE SYNTHESIS OF THIS ENZYME.
CELLS (0.7 mg DRY CELL WT./ml) WERE
CULTURED FOR 48 HRS. IN SNC BROTH WITH THE ABOVE
CARBON SOURCES AT 20 mM (PHB at 0.2 w/v). THE
HIGHEST ACTIVITIES WERE OBTAINED WITH PHB AND
3HB. SIGNIFICANT ACTIVITIES WERE OBTAINED WITH
N-ACETYLGLUCOSAMINE, MALTOSE, AND CERTAIN
ORGANIC ACIDS. GLUCOSE DID NOT SUPPORT ENZYME
SYNTHESIS, SUGGESTING THAT CATABOLITE REPRESSION
MIGHT BE INVOLVED.
SNC BROTH CONTAINING 0.2 PHB PLUS 0.5 GLUCOSE
WAS INOCULATED (10 v/v INOCULUM) AND INCUBATED
WITH AERATION AT 30?C. SAMPLES WERE WITHDRAWN AT
TIME INTERVALS AND ASSAYED FOR ENZYME ACTIVITY,
PHB CONTENT, GLUCOSE, AND CELL PROTEIN. PHB
DEGRADATION AND ENZYME SYNTHESIS BEGAN ONLY WHEN
GLUCOSE WAS COMPLETELY METABOLIZED, INDICATING
CATABOLITE REPRESSION.