or citrate phosphate buffer is used of no buffer at all, which is beneficial
for industrial application.
For all other experiments the acetate buffer was used to maintain
the desired pH. It should be noted, however, that acetic acid in
high concentrations inhibits growth and fermentation yields of
yeasts, such as S. cerevisiae and Pichia stipitis and inhibits fermentation
process itself. Acetic acid in its undissociated form cross
the plasma membrane and dissociates intracellularly, due to the
higher intracellular pH and exhibit cellular toxicity, therefore acetate
buffers of used concentrations are not suitable for fermentation
processes with certain yeasts (Hu et al., 2009; Huang et al.,
2012; Olsson and Hahn-Hägerdal, 1996). The use of the buffers
for the future laboratory experiments was necessary to maintain
the pH of experimental samples of suspensions, because all tested
waste materials increased the pH of the suspension formed. The
use of organic acids to adjust pH in the industrial process is unlikely
due to higher financial costs compared to mineral acids (e.g.
H2SO4) and bases (NaOH or KOH) as commonly used in distilleries
to adjust the pH.