Mineral Salt Broth Research Articles

Influence of cultural parameters on the depolymerization of a soluble lignite coal polymer by Pseudomonas cepacia DLC-07

A lignite coal-depolymerizing bacterium, Pseudomonas cepacia DLC-07, was grown in liquid media containing water soluble lignite coal. The coal substrate was soluble at pH 5.5, but had not been preoxidized with nitric acid. Bacterial coal depolymerization was monitored by high performance liquid chromatography (HPLC). Cells were grown on soluble coal in three media: mineral salts broth, peptone broth, and Sabouraud dextrose broth (SDB). In some experiments, media were supplemented with specific coal substructure model compounds, or a mixture of compounds, which served as potential inducers of coal-degradative enzymes. In one experiment, peptone broth contained Kraft lignin instead of coal. Uninoculated controls were included in all experiments. P. cepacia DLC-07 depolymerized coal in all experiments, but depolymerization was greatest in peptone-coal broth. Of ten coal substructure models examined, indole and p-coumaric acid measurably affected depolymerization. Their presence in SDB led to the appearance of distinctive peaks in HPLC chromatograms. P. cepacia further polymerized Kraft lignin into a product of higher molecular weight than the starting substrate. Spectrometric analyses showed that coal depolymerization was associated with attack on ester and ether bonds in the coal.

Rubratoxin production by penicillium rubrum when grown in a synthetic medium containing different sources of carbon and nitrogen

A sterile mineral salts broth was fortified with different additives, inoculated with conidia ofPenicillium rubrum P-13, and incubated quiescently for 14 days or with shaking for 3 to 5 days. Maximal fungal growth and rubratoxin production occurred when the broth contained 20% sucrose. Broth with 10% glucose, 10% fructose, 5% maltose, or 1% asparagine supported formation of substantial amounts of rubratoxin (52.9–78.5 mg/100 ml). When the broth was fortified with glucose plus lysine, arginine aspartic acid, cystine, ammonium citrate, or ammonium phosphate, moderate amounts (27.5–39.5 mg/100 ml) of rubratoxin and mycelium (0.1–1.5 g/100 ml) were produced. Presence in the broth of 5% galactose or starch resulted in accumulation of small amounts (22.2 and 24.6 mg/100 ml, respectively) of rubratoxin and mold tissue (0.70 and 0.5 g/ 100 ml, respectively). Whereas some toxin was recovered from mineral salts broth fortified with lactose or ribose, toxin was not recovered when the mold grew in broth containing mannitol or fumarate. With the exception of gluconate which supported some growth and toxin formation and ethanol which permitted formation of small amounts of toxin, other carbon sources resulted in little or no fungal growth and no toxin formation. Yields of rubratoxin decreased with an increase in amount of agitation or length of incubation ofP. rubrum cultures. Mold growth increased and toxin formation decreased with an increase in volume of culture.