Continuous culture for the bioproduction of glycerol and ethanol by Hansenula anomala growing under salt stress conditions

Abstract

Continuous cultures of Hansenula anomala were carried out in media at low water activity, resulting from NaCl addition. Three dilution rates were compared and it was shown that a clear steady state was only recorded for the lowest dilution rate tested (0.03 h −1 ), leading to a biomass concentration of 4.3 g L −1 . At 0.06 h −1 dilution rate, steady state was maintained for no more than 20 h and a clear washout was observed at 0.12 h −1 . The experimental ratio ethanol on glycerol produced at steady state (D=0.03 h −1 ) was similar to that previously recorded in batch culture in similar conditions after 30 h of growth, 7.8 and 7.9, respectively. The comparison of continuous culture to repeated batch culture was clearly in favour of the continuous culture, which led to significantly higher glycerol and ethanol production rates, 4.5 and 4 times higher than those recorded in repeated batch culture, respectively, even if significant amounts of glucose remained in the bleeding of the bioreactor.

Enhancement of ethanol production from synthetic medium model of hydrolysate of macroalgae

“…That also impacts cell growth and ethanol production and promotes glycerol 437 production [51]. Similar behavior was previously recorded with Hansenula anomala [37] …”

Isolation and Identification of Yeast Strains From Sugarcane Molasses, Dates and Figs for Ethanol Production Under Conditions Simulating Algal Hydrolysate

“…The fermentation of glucose, galactose, fructose, saccharose, lactose, xylose, maltose and arabinose was tested. The sugars were dissolved at 2 % (w /v) in the Wikerham medium (Djelal et al, 2012) containing in g.L -1 : Peptone 10, yeast extract 5, phenol red 24 mg. The tests were performed in Durham tubes, which were inoculated and incubated at 30°C for three weeks.…”

“…It was in accordance with the biomass decrease in the presence of salts, since maximum cell density (absorbance at 600 nm) was in the range 11-13 ( Figure 3) in the absence of salts and only in the range 1.3-1.9 in the presence of salts (Table 3). Osmotic pressure impedes yeast development and thus partially inhibits glucose assimilation (Djelal et al, 2012). A high osmotic pressure drives a passive water outflow through the cytoplasmic membrane to restore thermodynamic equilibrium, thus to a dehydratation (Blomberg, 2000).…”

Second-generation ethanol production by Wickerhamomyces anomalus strain adapted to furfural, 5-hydroxymethylfurfural (HMF), and high osmotic pressure

“…In S. cerevisiae, changes in internal metabolic fluxes that lead to the production of glycerol help to counter cell stress or adapt to stressful conditions such as osmotic pressure, high ethanol and CO 2 concentrations, among others (Pandey et al 2007). Glycerol production in response to environmental stress was also reported for W. anomalus, as this yeast survives in media at low water activity resulting from increasing NaCl concentrations in the culture medium by producing compatible solutes, like glycerol, arabitol, and trehalose (Djelal et al 2012).…”