Poly-β-hydroxybutyrate (PHB) is the intracellular lipid reserve accumulated by many bacteria. The most potent terrestrial bacterium Bacillus cereus SE-1 showed more PHB accumulating cells (22.1 and 40% after 48 and 72 h) than that of the marine Bacillus sp. CS-605 (5 and 33% after 48 and 72 h). Both the isolates harbored phbB gene and the characteristics C=O peak was observed in the extracted PHB by Fourier transformed infrared spectroscopy analysis. Maltose was found to be the most suitable carbon source for the accumulation of PHB in B. cereus SE-1. The extracted PHB sample from B. cereus SE-1 was blended with a thermoplastic starch (TS) and an increased thermoplasticity and decreased crystallinity were observed after blending in comparison to the standard PHB. The melting temperature (Tm), melting enthalpy (∆Hf), and crystallinity (Xc) of the blended PHB sample were found to be 109.4 °C, 64.58 J/g, and 44.23%, respectively.
Understanding
solid–water(vapor) interfacial systems is
relevant for both industrial and academic scenarios for their presence
in wide areas ranging from tribology to geochemistry. Using grand
canonical Monte Carlo simulations, we have investigated the role of
monovalent (lithium, Li+; sodium, Na+; and potassium,
K+) and divalent (magnesium, Mg2+; calcium,
Ca2+) cations on the structure and adsorption behavior
of water on mica surface. The water density adjacent to the surface
exhibits (a) oscillations due to hydration of surface cations
(interfacial layer), (b) followed by a thick liquidlike layer.
The thickness of the interfacial layer is strongly dependent on the
hydration shell size and hydration energy of surface ions. Water molecules
immediately next to the surface (contact layers) adsorb on ditrigonal
(hexagonal) cavities of mica surface and form an ordered structure.
The Li+, Na+, Mg2+, and Ca2+ surface ions are coadsorbed with water molecules on the ditrigonal
cavities due to their smaller hydration shell. Majority of water molecules
in the second contact layer hydrate the surface ions and, together
with the rest of the water molecules, form hydrogen bonds among themselves.
The structure of the water molecules in the third and subsequent layer
is random and more bulk liquidlike, except those molecules that hydrate
the surface ions. The adsorption isotherm of water on all ion-exposed
mica surface exhibits three regimes: (a) an initial rapid increase
in water loading for relative vapor pressure (p/p
0) ≤0.2 due to hydration of surface ions;
(b) followed by a linear increase between p/p
0 = 0.2 and 0.7, where the hydrogen bond formation
between the water molecules of the interfacial layer occurs; and (c)
exponential growth beyond p/p
0 = 0.7 due to thickening of the liquidlike layer. The water
loading on divalent-ion-exposed mica surface is higher compared to
the monovalent ions case. Although the divalent ions have higher hydration
energy, the fraction of water molecules hydrating the surface ions
is less compared to nonhydrating water molecules. We found that ion
hydration energy and size of hydration shell play a crucial role in
their structure adjacent to mica surface. At lower water loadings,
the surface ions form a hydration shell with surface bridging oxygens,
whereas at higher water content, the hydration preference is shifted
toward mobile water molecules. The detailed understanding obtained
from this work will be useful in identifying the role of ions in cloud
formation, nanotribological studies, and activities of biological
molecules and catalysts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.