An environmentally friendly and productive process for bioethanol production from potato waste

Table 2 Comparison of different processes using potato waste materials to produce ethanol

Raw materials	Substrate concentration (w/v)	Pretreatment method	Glucose concentration (g/L)	Ethanol concentration (g/L)	Glucan conversion (%)	Glucose to ethanol conversion (%)	Ethanol yield (g/g, dry weight)	Reference
Sweet potato residues	36 %	Enzymatic hydrolysis^a	168.13 ± 2.62	79.00 ± 0.87	68.34 ± 1.07	67.16 ± 0.74	0.23 ± 0.00	This study
Sweet potato residues	36 %	Enzymatic hydrolysis^b	153.46 ± 2.01	73.37 ± 1.87	62.37 ± 0.82	62.37 ± 1.59	0.21 ± 0.01	This study
Potato pulp	30 %	Hydrothermal pretreatment and enzymatic pretreatment^c	114	Less than 60	68	Less than 68	Less than 0.2	[48]
Potato peel waste	2 %	Enzymatic hydrolysis^d	18.48 ± 0.65	7.50 ± 0.28	–	–	–	[23]
Waste potato mash	–	Physical method^e	Less than 80	35	–	–	–	[24]
Potato peel + substandard mash	1:1	Enzymatic hydrolysis^f	–	48.6 ± 1.3	–	42.5	0.19	[57]
Potato tuber mash	1:1	Acid-catalysed hydrolysis^g	100	32.9	–	–	–	[20]
Potato peel waste	4 %	Acid-catalysed hydrolysis^h	18.15	6.97	–	–	–	[23]
Potato starch residue stream	–	Acid-catalysed hydrolysisⁱ	18.9	5.62 ± 0.21	–	–	–	[21]

^a4 FPU/g dry SPRs + 1000 PGU/g dry SPRs, 45 °C for 6 h, cellulase from T. reesei TX, pectinase was generously provided by Qingdao Vland Biotech Inc
^b6 FPU/g dry SPRs, 45 °C for 6 h, cellulase from T. reesei TX
^cHot water pretreatment, 121 °C for 20 min, 5 FPU/g dry weight, 50 °C for 48 h, enzyme from A. cellulolyticus
^d0.12 U/g dry weight at 85 °C for 1 h, enzyme from Termamyl 120 L, then 12 U/g dry weight at 44 °C for 2.5 h, enzyme from Viscozyme, and finally, 1 g Celluclast per g dry weight at 50 °C for 2 h
^eAgitation at 120 rpm for 3 h at a temperature chosen by the design based on a preliminary study
^fThe amount of enzyme, consisting of α-amylase + Pectinase + Enzyme complex, is 0.1 %. They were incubated at 50 °C for 21 h
^g60 min in 1 M HCl at 100 °C
^h0.5 M HCl, 121 °C for 15 min
ⁱ60 min in 1 % H₂SO₄ at 100 °C

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