## 2 Results and Discussion
### Influence of Contact Time on the Adsorption Process: Kinetic and Mass Transfer Studies
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Properties** & **Units** & **Values** \\ \hline S\({}_{\text{BET}}\)1  & 500 \\ d\({}_{\text{p}}\)2  & \(\text{A}\) (cm) & 260 (2.6 \(\times\) 10\({}^{-6}\)) \\ \(\rho_{\text{S}}\)3  & g\(\cdot\)cm\({}^{-3}\) & 1.01 \\ \(\rho_{\text{p}}\)4  & g\(\cdot\)cm\({}^{-3}\) & 0.44 \\ \(\text{D}\)5  & \(\mu\)m (cm) & 550 (5.5 \(\times\) 10\({}^{-2}\)) \\ \(\text{R}_{\text{P}}\)6  & \(\mu\)m (cm) & 275 (2.75 \(\times\) 10\({}^{-2}\)) \\ \(\text{V}_{\text{p}}\)7  & cm\({}^{3}\cdot\)g\({}^{-1}\) & 1.3 \\ \(\epsilon_{\text{P}}\)8  & Dimensionless & 0.56 \\ \(\text{T}\)9  & Dimensionless & 3.70 \\ \(\text{S}_{\text{EXT}}\)9  & m\({}^{2}\cdot\)g\({}^{-1}\) & 25 \\ \(\text{\rho}_{\text{solution}}\)1  & g\(\cdot\)cm\({}^{-3}\) & 1.003 \\ \(\text{H}_{\text{solution}}\)1  & g\(\cdot\)cm\({}^{-1}\cdot\)s\({}^{-1}\) & 9.3 \(\times\) 10\({}^{-3}\) \\ \(\text{\rho}_{\text{suspension}}\)10  & g\(\cdot\)cm\({}^{-3}\) & 1.007 \\ \(\text{H}_{\text{suspension}}\)11  & g\(\cdot\)cm\({}^{-1}\cdot\)s\({}^{-1}\) & 1.08 \(\times\) 10\({}^{-2}\) \\ \(\text{V}_{\text{M}}\)12  & cm\({}^{3}\cdot\)mol\({}^{-1}\) & 47407.5 \\ \(\text{D}_{\text{AB}}\)13  & cm\({}^{2}\cdot\)s\({}^{-1}\) & 2.19 \(\times\) 10\({}^{-5}\) \\ \(\text{Sc}\)14  & Dimensionless & 489.7 \\ \(\text{Re}\)15  & Dimensionless & 7692.4 \\ \(\text{Sh}\)16  & Dimensionless & 415.9 \\ \(\text{K}_{\text{SL}}\)17  & cm\(\cdot\)s\({}^{-1}\) & 1.66 \(\times\) 10\({}^{-1}\) \\ \(\text{D}_{\text{eff}}\)17  & cm\({}^{2}\cdot\)s\({}^{-1}\) & 3.31 \(\times\) 10\({}^{-6}\) \\ \(\text{Bi}_{\text{m}}\)18  & Dimensionless & 105.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of the support, enzyme solution and suspension solid–liquid for the determination of fluid mechanics and mass transfer parameters of the adsorption process (preparation of the heterogeneous biocatalyst). with flavor properties via direct esterification of short-chain starting materials such as octanoic acid (8 carbon atoms) and several alcohols--from 1 carbon atom (methanol) to 7 carbon atoms (benzyl alcohol). In this case, excellent external mass transfer of short-chain starting materials from the reaction mixture (warranted by a vigorous mechanical stirring-240 rpm) to the internal microenvironment of the biocatalyst is expected, thus exhibiting high catalytic performance in synthetic short-chain esters production, as follows. Comparative Performance of Soluble or Immobilized Lipase Eversa(r) Transform 2.0 on Flavor Esters Production via Esterification  
The catalytic performance of immobilized lipase Eversa(r) Transform 2.0 on PSTy-DVB beads in the direct esterification of octanoic acid with different short-chain alcohols in solvent-free systems was evaluated and compared with its soluble form. The different chemical structures (linear, branched or aromatic chains) and polarity of short-chain alcohols, as well as different rheological properties of the reaction media, can strongly influence the mass transfer processes (external and internal mass transfer) and catalytic performance of the enzyme [50; 51]. Moreover, the form of the biocatalyst (soluble or immobilized lipase) can also alter the polarity and partitioning effects that results in the distinct accessibility of starting materials to the enzyme microenvironments [50]. In this study, the polarity of the different alcohols was defined based on their Log P values, logarithm of partition coefficient in an 1-octanol/water biphasic system [8]. In fact, different catalytic performances by using different alcohols or lipase forms were achieved, as shown in Figure 4A-F. In general, a linear profile for all reaction systems using both biocatalyst forms (soluble or immobilized lipase) up to 50% of acid conversion can be observed, thus suggesting lack of diffusional problems. However, the different reaction times to achieve such acid conversion percentage values can be verified due to different properties for each reaction mixture, as expected.