Use of Nonspecific, Glutamic Acid-Free, Media and High Glycerol or High Amylase as Inducing Parameters for Screening Bacillus Isolates Having High Yield of Polyglutamic Acid

Table 3

(a) Effect of physiological state of cells of Bacillus T. on production of PGA^a in non glutamic acid containing media. (b) Effect of glutamic acid supplementation on yield of PGA^a by Bacillus strains.

(a)

Inoculum medium (broth)	Luria Bertanii		Synthetic
Inoculum age (h)	24–36	72	24–36	72
Vegetative cells present/2 cm^2 square smear	800	112	360	38
Sporulated cells present/2 cm^2 square smear	0	920	0	460
Polymer^c (g/l) in broth (Inoculum used: 4% v/v)	7.1	4.5	4.5	2.1
Polymer^c (g/l) in broth (Inoculum used: 20% v/v)	6.5		5.4

(b)

Synthetic medium^b	With glutamic acid (20 g/l)		Without glutamic acid
PGA producing culture	Bacillus K.	Bacillus T.	Bacillus K.	Bacillus T.
PGA on solid medium	+	+	+	+
PGA in broth (g/l)^c	30 (±4.5)	11 (±3.4)	7 (±1.1)	2.5 (±1.1)

Polymer was either observed on solid medium as mucoid colonies (+) or extracted from broth cultures incubated on rotary shaker (180 rpm) using 3x volumes of acetone. Values are of dry weight of precipitated polymer, SD in parentheses.
^bProduction medium: 20 g sodium citrate/l, 40 g glycerol/l in Bushnell and Hass medium base (pH 7). For solid medium 25 g agar/l was added.
^cFor broth culture, 50 mL medium in 250 mL Erlenmeyer flasks was inoculated (6% inoculum v/v after centrifugation and discarding supernatant) with culture (OD = 1) and incubated for 24 to 96 h at 30°C. Polymer was extracted using 3x volumes of acetone, dried at 60°C.