Table 2 Production performance of the constructed HBCs producing strains in this study and some previously reported HBCs producing strains ^a .

Strains	Substrates	Substrate molar conversion rate (%)	Metabolites ^b	Molar yield (%)
XIIΔhsd4A	phytosterols, 40 g/l	70–73 in 144 h	1,4-HBC	39–40
			4-HBC	18–20
			ADD	1–2
XIIΔhsd4A-p261kstD1	phytosterols, 40 g/l	70–73 in 144 h	1,4-HBC	54–57
			4-HBC	4–7
			ADD	1–2
XIIΔhsd4AΔkstD1	phytosterols, 40 g/l	63–66 in 144 h	4-HBC	33–35
			1,4-HBC	15–18
			9-OHHBC	3–4
			AD	1–2
XIIΔhsd4AΔkstD13	phytosterols, 40 g/l	63–66 in 144 h	4-HBC	36–37
			1,4-HBC	13–15
			9-OHHBC	3–5
			AD	1–2
XIIΔhsd4AΔkstD123	phytosterols, 40 g/l	60–62 in 144 h	4-HBC	47–49
			9-OHHBC	2–3
			1,4-HBC	1–2
			AD	1–2
MNΔhsd4AΔkstD123	phytosterols, 40 g/l	50–54 in 144 h	9-OHHBC	30–32
MNΔhsd4AΔkstD123	phytosterols, 40 g/l		9-OHAD	14–15
Mycobacterium sp. NRRL B-3683³⁰	Tall oil phytosterols 1 g/l	n.m. in 192h	1,4-HBC	3
			4-HBC	Trace
			ADD	48
			AD	1
Mycobacterium sp. 2-4M¹⁰	sitosterol, 5 g/l	95–97 in 120 h	9-OHHBC	1.5–1.6
			4-HBC	n.m. ^c
			9-OHAD	48–50
			AD	21–22
			9-HCBC	0.5–0.7
			9-OHT	0.10–0.14
M. parafortuitum complex MCI 0617¹¹	cholesterol 10 g/l	99 in 160 h	1,4-HBC	62
			4-HBC	5
			ADD	0.8
M. neoaurum Mut_MN-kstD1&2&3⁴	phytosterols, 15 g/l	70–75 in 144 h	4-HBC	1–2
			9-OHAD	50–55
			AD	10–15

^aThe biotransformation was performed in a resting cell transformation system supplemented with 40 g/l of phytosterols for 144 h at 30 °C. Data are obtained from three independent experiments performed upon triplicate samples.
^bAbbreviations: AD, androst-4-ene-3,17-dione; ADD, androst-1,4-dien-3,17-dione; 9-OHAD, 9α-hydroxy-androst-4-ene-3,17-dione; 4-HBC, 22-hydroxy-23,24-bisnorchol-4-ene-3-one; 1,4-HBC, 22-hydroxy-23,24-bisnorchol-1,4-dien-3-one; 9-OHHBC, 9,22-dihydroxy-23,24-bisnorchol-4-ene-3-one; 9-OHT, 9α-hydroxy-4-androsten-17β-ol-3-one; 9-HCBC, 9α-hydroxy-22-carboxy-23,24-bisnorchol-4-en-3-one. The structural information of 9-OHT and 9-HCBC is provided in Fig. S7.
^cn.m., not mentioned.

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