# Exploring an Integrated Manure-Sewater System for Sustainable Cyanobacterial Biomass Production
## 3 Results
### Growth Response of Cyanobacteria to Manure and Seawater Media  
Differences in pH were observed between cow manure, pig manure and chicken manure. Before the cyanobacteria were cultured, the chicken manure was slightly acidic (pH 6.87), while pig manure and cow manure were basic (pH 8.76 and 9.43, respectively). After the cyanobacterial strain was grown for approximately 21 days, the pH value of the cultures increased for BG11, cow manure-seawater, and pig manure-seawater media, while there was no pH change in the chicken manure-seawater medium (Figure 4).  
The cyanobacterial strain HSaC biomass production was significantly (\(p<0.05\)) different among the integrated manure-seawater media. The highest (33.26 mg/mL) biomass was obtained from cow manure with diluted seawater (10 dS/m), while the lowest biomass was from chicken manure with all seawater treatments and pig manure with distilled water (Figure 5). The biomass yield obtained from BG11 with seawater was higher than that obtained from the pig and chicken manure with seawater (Figure 5).  
Figure 3: HSaC cyanobacterial chlorophyll content as influenced by different NaCl salt concentration (0 mM, 60 mM, 120 mM, 180 mM, 240 mM and 300 mM). The error bars represent standard deviation (SD). The data are the mean of three replicates.  
in Figure 6, Figure 7 and Figure S2. On the other hand, a significant difference in biomass yield and chlorophyll a was observed between the natural seawater (SN) and artificial seawater (SA) treatments (Figures 6 and 7).  
Figure 6: Effect of both natural and artificial seawater in cow manure media on HSaC cyanobacterial biomass. DW = distilled water with cow manure, 10N = natural seawater (EC, 10 dS/m) with cow manure, 10A = artificial seawater (EC, 10 dS/m) with cow manure, SA = artificial seawater with cow manure and SN = natural seawater with cow manure. The error bars represent standard deviation (SD). The data are the mean of three replicates. Differing letters indicate significant differences in means of HSaC cyanobacterial biomass in pairwise comparisons (Tukey’s test \(p<0.05\)) for each treatment by LSD.  
Figure 7: Effect of natural and artificial seawater with cow manure on the chlorophyll content of salt-tolerant cyanobacteria (HSaC). DW = distilled water with cow manure, 10N = natural seawater (EC, 10 dS/m) with cow manure, 10A = artificial seawater (EC, 10 dS/m) with cow manure, SA = artificial seawater with cow manure and SN = natural seawater with cow manure. The error bars represent standard deviations (SDs). The data are the mean of three replicates. Differing letters indicate significant differences in means of HSaC cyanobacterial chlorophyll content in pair wise comparisons (Tukey’s test \(p<0.05\)) for each treatment by LSD.  
The photosynthetic pigment (chlorophyll a) content (Figure S3) and biomass yield (Figure 8) of cyanobacterial strain LC were significantly (\(p<0.05\)) different among the cow manure-seawater media treatments. The highest biomass yield (35.47 mg/mL) of strain LC was obtained from cow manure with diluted natural seawater at an EC of 0.5 dS/m, while the lowest value (10.66 mg/mL) was from cow manure with diluted seawater at an EC of 1.5 dS/m (Figure 8).