Microbial degradation is directly affected by Tm ,
i.e. the lower the Tm , the higher the
biodegradation of a toxicant such as free cyanide
[31-33]. Beta vulgaris consist
of 9.56 % carbohydrates, with betalains, phenolic compounds, including
trace elements and minerals accounting for a larger percentage
[34,
35]. The presence of betalains and
phenolic compounds influence the microbial growth in BA samples since
they degrade under different bioreactor operating conditions
[36] from that of free cyanide,
resulting in a slightly higher molecular weight of the F.
oxysporum and thus, a higher Tm for BA samples.
Similarly, interactions of molecular chains affect the change of
enthalpy \((H)\) in melting with the internal energy accounting for the
flexibility or otherwise of the samples studied, thus affecting the
change of entropy \((S)\) in melting
[37]. The highest \(H\) in melting
for BCN samples was an indication of highest molecular interactions
during free cyanide biodegradation.
Tan et al. [30] reported glass
transition on reversible heat flow profile of MDSCTMafter the onset temperature which overlapped with the peak temperature.
It was presumed that this was due to changes in the state of the starch
molecules i.e. from being highly confined within the granular packing,
to being disentangled as the order in which the molecules are arranged
changed as the transition occurred. Glass transition could also be due
to structural transitions of cellular materials at temperatures below
freezing point of pure water including the influence of the underlying
heating rate, modulation period and amplitude
[17,
27]. There was no glass transition onF. oxysporum grown on glucose i.e. GA, this is similar to
the previous report on the heat capacity of starch and glucose
[14,
16]. It was evident that the substrate
from which the biomass materials were formed, played a major role in the
phase transition as can be seen that only cultures grown on Beta
vulgaris (BA and BCN), had a glass transition.