Maximizing biohydrogen production from watermelon peels using Clostridium butyricum NE133: a statistical optimization approach with Plackett–Burman and Box–Behnken designs

Table 7 Gas-chromatography analysis for WMP fermentation media extract before and after fermentation

Medium	Compound	Formula	Retention time	Area	Area (%)
Pretreated watermelon peels control medium	Bis(2-ethylhexyl) phthalate	C₂₄H₃₈O₄	47.22	49,648,917.63	32.51
	9,12-Octadecadienoic acid (Z, Z) (Linoleic acid)	C₁₈H₃₂O₂	40.91	2,366,643.10	1.55
	Octadecanoic acid (Stearic acid)	C₁₈H₃₆O₂	37.75	12,892,066.34	8.44
	Hexadecanoic acid (Palmitic acid)	C₁₆H₃₂O₂	41.31	10,207,942.17	6.68
	Hexadecadienoic acid, methyl ester	C₁₇H₃₀O₂	41.07	1,923,123.81	1.26
	Oleic acid, eicosyl ester (CAS)	C₃₈H₇₄O₂	49.34	1,334,310.29	0.87
	Hexadecatrienoic acid, methyl ester, labeled with carbon13(CAS)	C₁₇H₂₈O₂	42.08	533,174.46	0.35
	Rhodoxanthin	C₄₀H₅₀O₂	48.43	721,462.42	0.92
	Lucenin 2	C₂₇H₃₀O₁₆	50.49	695,574.96	0.85
	Lycoxanthin	C₄₀H₅₆O	50.80	2,767,267.82	1.81
Optimized watermelon peels spent medium	Bis(2-ethylhexyl) phthalate	C₂₄H₃₈O₄	47.29	14,612,282.90	21.79
	Palmitic acid	C₁₆H₃₂O₂	41.41	867,259.05	1.29
	9Hexadecenoic acid, 9octadecenyl ester, (Z, Z) (CAS)	C₃₄H₆₄O₂	51.51	1,366,743.69	2.04
	9Octadecenoic acid (Z), 9octadecenyl ester, (Z)(CAS)	C₃₆H₆₈O₂	53.80	675,950.07	1.01
	Butyric acid, 4 hydroxy2 methylene	C₅H₈O₃	49.90	1,360,464.37	2.03
	Z, Z3,15Octadecadien1-ol-acetate	C₂₀H₃₆O₂	52.80	705,827.33	1.05

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