# Effect of Ultrasound on Fermentation of Thick Molasses Worts by Distiller's Yeast
###### Abstract
Notwithstanding the importance of sugars during the fermentation process, it is noteworthy that the effectiveness of this process is influenced by more than just saccharides. Every organism requires sufficient water and nutrients to grow and conduct the fermentation process efficiently. Following the carbon source, another necessary component is assimilable nitrogen. As most yeast species cannot fix atmospheric nitrogen, it must be supplied either in organic nitrogen (as amino acids, urea, or other compounds) or inorganic nitrogen (as ammonium salts). This element is pivotal in biosynthesis, forming various proteins, including enzymes [16]. The subsequent essential component for effective fermentation is the proper amount of inorganic ions. The requirement for millimolar concentrations of elements such as phosphorus, sulphur, potassium, and magnesium is \begin{table}
\begin{tabular}{c c} \hline
**Raw Material** & **Theoretical Ethanol Yield [L/100 kg]** \\ \hline Corn grain & 400 \\ \hline Sugarcane juice & 70 \\ \hline Sugarcane molasses & 205 \\ \hline Cassava roots & 180 \\ \hline Sweet potato & 160 \\ \hline \end{tabular}
\end{table} 
Table 1: Ethanol yield from different raw materials [8; 10]. essential. Also, micromolar concentrations of sodium, calcium, iron, cobalt, zinc, copper, manganese, nickel, and selenium are required [17]. Another critical factor in the fermentation process is the concentration of ethanol, the end product of primary importance, which can exert inhibitory effects on cells. Increased ethanol concentrations can harm cell growth and fermentation rate, so their levels must be closely monitored. Higher ethanol concentrations can denature various enzymes, inhibit sugar and amino acid transport systems, and contribute to thermal death. Finally, it is essential to note that ethanol can modify cell membranes, resulting in changes to their permeability and structural organisation [18]. Sugar is the principal substrate for microorganisms during the alcoholic fermentation process; thus, its concentration in the wort is significant--generally, an increase in sugar concentration results in an increase in ethanol, a fermentation product. However, a high sugar concentration can have a detrimental effect on the fermentation process, potentially leading to toxicity in microbial cells and the occurrence of hyperosmotic stress. Increases in sugar concentration may be attributable to sugar accumulation within the cell, consequent to the inactivation of sugar transport systems [19]. The drive towards production efficiency and the need to address growing demands has compelled manufacturers to adopt contemporary methods to enhance fermentation efficiency. Many techniques have been proposed to address not only the efficiency of the process but also the quality and safety of end products. Among these novel techniques, thermal processing, encompassing microwave heating, radiofrequency heating, ohmic heating, pulsed electric field, and ultrasound treatment, has emerged as up-and-coming areas of research [20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30]. Ultrasound can be defined as mechanical pressure waves with a frequency that exceeds the audible level (i.e., over 20,000 Hz). A piezoelectric transducer is a material that emits and receives ultrasound waves, thereby converting electrical energy into vibrational sound energy [31]. Ultrasound is ubiquitous in numerous industrial sectors, including chemical, bioprocessing, food processing, and the pharmaceutical and medical industries. In these sectors, both high-frequency and low-frequency ultrasound are utilised. For instance, in the food industry, high-frequency ultrasound (>1 MHz) is employed for non-destructive methods of control and quality assurance, while low-frequency ultrasound (approx. 20 kHz-1 MHz) is typically used for the intensification of a process [32]. The generation of particle displacement results from ultrasonic waves passing through a medium, with the wave source inducing a succession of compression and rarefaction phases [33].