TABLE 2.

Enhancement of Cr(VI) reduction using different electron donors by different microorganisms.

Microorganisms	Electron donors	Aerobic/anaerobic	Concentrations of electron donor (a) and Cr(VI) (b)	Chromium reduction (%)		References
				Without electron donor	With electron donor
Halomonas chromatireducens AGD 8–3	Acetate	Aerobic	(a) 20 mM	0	>90	Shapovalova et al., 2009
			(b) 30 mg/L
Halomonas smyrnensis KS802	Galactose	Aerobic	(a) 4%	82.5	100	Biswas et al., 2018
			(b) 2 mM
Bacillus methylotrophicus	Reduced glutathione	Aerobic	(a) 20 mM	89.8	94.5	Mala et al., 2015
			(b) 200 μM
Ochrobactrum intermedium Rb-2	Gluconate	Aerobic	(a) 1%	<95	99	Batool et al., 2012
			(b) 1,000 mg/L
Enterobacter sp. DU17	Glucose	Aerobic	0.2%	59	100	Rahman and Singh, 2014
	fructose		100 mg/L		100
Pseudomonas aeruginosa CRM100	Citrate	Anaerobic	(a) 4.0 g/L	0	99.73	Salamanca et al., 2013
	glycerol		(b) 100 mg		88.4
Pelosinus sp. HCF1	Lactate	Anaerobic	(a) 20 mM	<12	>90	Beller et al., 2013
			(b) 45 μM
Arthrobacter sp. LLW01	Lactate	Aerobic	15 mM	0	80	Field et al., 2018
			50 μM
Microbial consortium	H2: CH4	Anaerobic	1:1 ratio	0	95.5	He et al., 2020
			10 mg/L Cr(VI)
Flexivirga alba ST13T	Molasses	Aerobic	0.4%	<10	>95	Ikegami et al., 2020
			0.5–0.6 mg/L
Stenotrophomonas sp. WY601	Lactose, fructose, and glucose	Anaerobic	2%	0	68–80	Liu et al., 2019a
			2,500 mg/L
Bacillus sp. M6	Glycerol	Aerobic	0.1 mM/L	3.4	69.2	Li et al., 2019a
			20 mg/L
Microcosms	Yeast extract	Aerobic	200 mg/L	<10	100	Ancona et al., 2020
			1,000 μg/L
Bacillus sp. CRB-B1	Fructose	Aerobic	10 g/L	0	89.54	Tan et al., 2020
			100 mg/L
Bacillus cereus	NADH,	Aerobic	1 g/L	40	91.52,	Murugavelh and Mohanty, 2013
	NADPH		60 mg/L		96.54
Lysinibacillus fusiformis ZC1	Acetate, NADH	Aerobic	1%	21	92.4 92.0	He et al., 2011
			0.1 mM
Intrasporangium sp. Q5–1	Acetate	Aerobic	0.5 mM/L	75	95	Yang et al., 2009
			0.2 mM
Oceanobacillus oncorhynchi W4	Glycerol	Aerobic	3 g/L	<10	72.3	Zheng et al., 2019
			10 mg/L