Among these varied methods, this research
presents this procedure of pretreating with HCl instead of other
acids and methods and may possibly suggest that the higher yield
obtained here could be as a result of late addition of some of the
enzymes which increased the concentration of the reducing sugar.
Akacharanya et al. has reported the ethanol production of 9.9 g/L
from cassava starch pulp using enzymatic hydrolysis only and
equally produced 11.9 g/L of ethanol using H2SO4 pretreatment and
cellulase [30]. Torget et al. reported that pretreatment of cassava
residue with H2SO4 and hot water under pressure enhanced the
digestibility of the remaining solid cellulose but this research has
shown us that HCl is a better acid that disrupted more of the
complex cellulosic matrix thereby liberating more of the starch
granules [31,32]. Some researchers reported optimum fermentation
conditions of 30 C and pH 3.5 for higher yield of ethanol and
argued that higher temperature reduced the ethanol yield using
sugar cane molasses [33]. In this case, we applied pH of 4.6 and
temperature of about 45–50 C which may not be the optimum
conditions placing this process at a higher yield when the
conditions are optimized.