Evolutionary engineering of Lactobacillus bulgaricus reduces enzyme usage and enhances conversion of lignocellulosics to D-lactic acid by simultaneous saccharification and fermentation

Table 2 Comparison of cellulose conversion in EH and SSF experiments at different conditions

Process	Total Solid loading (% w/v)	D-LA (g/L)^#	Cellulose to D-LA conversion (%)	Cellulose to glucose conversion (%)^#
EH 15FPU/50 °C/pH 4.5	10		57.31^#	66.64 ± 1.23
EH 15FPU/45 °C/pH 5.5	10		52.13^#	60.62 ± 1.43
EH 5FPU/45 °C/pH 5.5	10		43.07^#	50.08 ± 1.05
EH 5FPU/37 °C/pH 5.5	10		41.47^#	48.22 ± 0.71
Batch SSF (L. bulgaricus WT) 5FPU/37 °C/pH 5.5	5	12.54 ± 0.53	49.11	57.11^*
Batch SSF (L. bulgaricus ET45) 15FPU/45 °C/pH 5.5	10	32.37 ± 0.44	63.4	73.72^*
Batch SSF (L. bulgaricus ET45) 5FPU/45 °C/pH 5.5	10	30.6 ± 0.61	59.93	69.68^*
Batch SSF (L. bulgaricus ET45) 5FPU/45 °C/pH 5.5	5	15.02 ± 0.33	58.83	68.41^*
Batch SSF (L. bulgaricus ET45) 3FPU/45 °C/pH 5.5	5	11.82 ± 0.31	46.3	53.84^*
Pulse-fed SSF (L. bulgaricus ET45) 5FPU/45 °C/pH 5.5	35	108.58 ± 1.75	60.76	70.65^*

^#Estimated cellulose to D-LA conversion = Cellulose to glucose conversion*Y_D-LA/Glucose
^*Estimated cellulose to glucose conversion = Cellulose to D-LA conversion/Y_D-LA/Glucose
Y_D-LA/Glucose = 0.86, calculated from independent SHF experiments at 45 °C and pH 5.5 (Table 1)
^#Measured values are mean ± SD

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