# Enhanced Enzymatic Degradability of Livestock Blood Pretreated with Ultrasonic Technique
## 4 Conclusions  
The aim of this study is to determine the feasibility of converting Livestock blood, a major Livestock organic waste whose treatment is highly challenging due to its high pollution potential and rapid decomposition, into an environmentally safe and high-quality Liquid amino acid fertilizer for agricultural use. Doing so would also reduce waste accumulation and pollution.  
1. Ultrasound pretreatment resulted in the improved enzymatic hydrolysis of the proteins in Livestock blood, as evidenced by the high hemoglobin solubilization rate (97.6%) of the ultrasound-treated blood samples; it also resulted in particle size reduction and pathogen elimination.
2. Protein hydrolysis experiments using different types of enzymes showed that Flavourzyme(r), an exo-type enzyme, exhibited the highest amino acid conversion efficiency. However, considering the relatively Lower cost-effectiveness of exo-type enzymes, especially for Large-scale processes, we determined the optimal condition to be the combination of the endo-type enzyme Savinase(r) and the exo-type enzyme Flavourzyme(r). This combination yielded an amino acid conversion rate similar to that achieved with the single use of Flavourzyme(r). Subsequent enzymatic hydrolysis experiments conducted on ultrasound-treated and untreated blood under the optimal conditions revealed that the amino acid concentration in ultrasound-treated blood reached 54.6 mg/mL, a nearly 4.2-fold increase compared to 13.1 mg/mL in untreated blood. This finding demonstrates that the ultrasonic treatment of Livestock blood enhances proteolytic hydrolysis efficiency, particularly when using a combination of endo- and exo-type enzymes, resulting in a substantial increase in amino acid conversion.
3. As enzymatic hydrolysis progressed, the viscosity of Livestock blood gradually decreased. Monitoring the agitator torque to gauge the reduction in applied physical force revealed a significant correlation between biological factors, such as protein and amino acid concentrations, and the mechanical factor, torque. Thus, it was confirmed that measuring torque during enzymatic reactions can be utilized to evaluate the extent of enzymatic reactions and thus serve as an indicator of reaction progress.  
Conceptualization, Y-W.J.; methodology, M-J.J.; validation, Y-W.J. and M-J.J.; formal analysis, M-J.J.; investigation, M-J.J. and Y-W.J.; writing--original draft preparation, Y-W.J.; writing--review and editing, Y-W.J.; supervision, Y-W.J.; project administration, Y-W.J.; funding acquisition, Y-W.J. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Korea Environment Industry & Technology Institute (KEITI) through the Development of Demonstration Technology for Converting Unconventional Waste Biomass to Energy project funded by the Korea Ministry of Environment (MOE) (RE20201941). And this research was also supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Korea Ministry of Trade, Industry & Energy (MOTIE) (20213030040070).  
Figure 6: Correlation between stirrer torque and (**a**) protein concentration and (**b**) amino acid concentration.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** The authors declare no conflicts of interest.