## 3 Results
### Effects of Starter Culture on Physicochemical Properties and Microbial Counts of Shrimp Paste  
The results of microbial counts are shown in Figure 5A,B. The total aerobic mesophilic bacterial counts on PCA agar plates grew gradually during the first 7 days and decreased gradually until the end of fermentation in both control and test groups. The highest bacterial counts in the control (\(7.47\log_{10}\) CFU/g) and test (\(7.75\log_{10}\) CFU/g) groups were both obtained on Day 7. The lactic acid bacteria (LAB) count of both control and test groups increased to the maximum value of 6.14 \(\log_{10}\) CFU/g and 6.37 \(\log_{10}\) CFU/g on Days 28 and 14, respectively, and then gradually decreased to 5.98 \(\log_{10}\) CFU/g on Day 35. From Day 0 to Day 21, both the total aerobic mesophilic bacteria and LAB counts of the test  
Figure 3: Comparative analysis of interspecies correlation of bacterial genus in control (**A**) and test (**B**) group. Correlations between bacteria are represented by lines between nodes. The red and green lines refer to positive and negative correlations, respectively.  
group were consistently higher than those of the control group, with a difference of no more than 0.5 log\({}_{10}\) CFU/g.  
Figure 4: Content of putrescine (**A**), cadaverine (**B**), histamine (**C**) in shrimp paste samples and Pearson correlation analysis between bacteria genus and BAs in control (**D**) and test (**E**) groups. * 0.01 \(<p\leq\) 0.05, ** 0.001 \(<p\leq\) 0.01.  
Figure 5: Microbiological and physicochemical characteristics of shrimp paste samples. (**A**) total aerobic bacterial count. (**B**) lactic acid bacteria count. (**C**) pH values. (**D**) Amino-acid nitrogen (AAN) content. (**E**) Total volatile base nitrogen (TVB-N) content.  
To investigate the impact of _T. muratiticus_ on the physicochemical quality of shrimp paste, the pH values, total volatile base nitrogen (TVB-N), and amino-acid nitrogen (AAN) concentrations of shrimp paste throughout the fermentation were measured, and the results are presented in Figure 5C-E. The initial pH values of the control and test groups were both 7.9 (Figure 5C). The pH levels of shrimp paste first dropped to 7.6-7.7 and then quickly rose to 8.0. There was consistently more AAN present in the test group than in the control group throughout the whole fermentation. The content of AAN was measured since it was an indicator of the degree of fermentation of shrimp paste. The initial content of AAN in both groups was about 1.15 g/100 g (Figure 5D). The AAN content first increased to a relatively stable level and then decreased to 1.13 and 1.21 g/100 g in the control and test group, respectively. When compared to the control group, the AAN level in the test group was consistently higher. To assess the degree of amino-acid degradation, the content of TVB-N was examined throughout the fermentation process. The TVB-N concentrations of shrimp paste samples were about 170 mg/100 g before the fermentation began (Figure 5E). The TVB-N accumulated gradually in both batches throughout the fermentation processes and upon 35 days of fermentation, the values in the control and test group reached 252 and 240 mg/100 g, respectively. The TVB-N concentrations in both batches were lower than the limit (450 mg/100g) of the Chinese commercial standard for shrimp sauce (SB/T 10525-2009).