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Biomedical subjects

A Leduy

Publications and source records attributed to A Leduy.

4 recordsLinked to original sources
PubMed1989

Effect of growth conditions and trehalose content on cryotolerance of bakers' yeast in frozen doughs.

The cryotolerance in frozen doughs and in water suspensions of bakers' yeast (Saccharomyces cerevisiae) previously grown under various industrial conditions was evaluated on a laboratory scale. Fed-batch cultures were very superior to batch cultures, and strong aeration enhanced cryoresistance in both cases for freezing rates of 1 to 56 degrees C min. Loss of cell viability in frozen dough or water was related to the duration of the dissolved-oxygen deficit during fed-batch growth. Strongly aerobic fed-batch cultures grown at a reduced average specific rate (mu = 0.088 h compared with 0.117 h) also showed greater trehalose synthesis and improved frozen-dough stability. Insufficient aeration (dissolved-oxygen deficit) and lower growth temperature (20 degrees C instead of 30 degrees C) decreased both fed-batch-grown yeast cryoresistance and trehalose content. Although trehalose had a cryoprotective effect in S. cerevisiae, its effect was neutralized by even a momentary lack of excess dissolved oxygen in the fed-batch growth medium.

Journal Article↗
PubMed1984

Peat hydrolysate medium optimization for pullulan production.

Peat hydrolysate, a diluted acid-autoclaved extract of peat, was used as a substrate for the production of the extracellular polysaccharide pullulan by three strains of Aureobasidium pullulans, 140B, 142, and 2552. It was found that the addition of (NH(4))(2)SO(4) and K(2)HPO(4) as sources of nitrogen and phosphate, respectively, is not necessary for the polysaccharide production. The economically optimized culture medium for large-scale production of pullulan contains peat hydrolysate, 0.05% NaCl, 0.02% MgSO(4), and 0.01% antifoam FG-10. The initial pH of peat hydrolysate medium is adjusted to its optimum value of 6.0 with Ca(OH)(2). The total ingredient cost for the production of each kilogram of pullulan with optimized medium is only 1/10 of that with the nonoptimized medium. In this study, a zero cost for peat hydrolysate was assumed, since it is an effluent of the peat and peat processing industries.

Journal Article↗
PubMed1979

Utilization of seawater-urea as a culture medium for Spirulina maxima.

The possibilities of utilization of seawater enriched with ureas as the culture medium for a blue-green alga, Spirulina maxima, were investigated. Pretreatment by precipitation with NaHCO3 and (or) Na2CO3 was found essential to remove the excess amounts of Ca2+ and Mg2+ present in seawater prior to cultivation. A culture medium as good as the synthetic medium reported in the literature for the growth of S. maxima was obtained after treating seawater with NaHCO3 (19.2 g/L) at pH 9.2 and 35 degrees C for 2 h, filtering to remove precipitates, and enriching with K2HPO4 (0.5 g/L), NaNO3 (3.0 g/L), and FeSO4 (0.01 g/L). The same results were obtained by substituting a small amount (0.2 g/L or less) of either crystalline or polymerized urea for the NaNO3 in the above medium. Growth of S. maxima was inhibited at higher concentration of urea in the culture medium. The inhibition effect was due to the partial decomposition of urea into ammonia in alkali medium. Tests conducted on the 130-L cultivation open pond also confirmed that the seawater-urea medium supports growth of S. maxima as well as the best known synthetic medium.

Culture Media↗