Ingenieur Vol. 75 ingenieur July 2018-FA - Page 60

INGENIEUR Figure 1: Scheme of SSF where saccharification and fermentation occurs in the same tank. juice, respectively. Since Malaysia has the same geographic latitude and seasonal conditions as Brazil, we could follow the same strategies in utilising agricultural waste as a biofuel. However, there are continuous debates about first generation biofuel, which utilises food sources as a fuel. The possible connection between ethanol production and food price inflation can occur in two ways, either by reallocating produced food crops to fuel production (e.g. sugarcane being allocated to ethanol rather than to sugar), or by diverting agricultural land from food crops to energy crops (e.g. rice crops being substituted by corn or sugarcane). But if the biofuel crops are cultivated only on unused or marginal land, the impact on food prices would be minimal. In Malaysia, the projected biomass waste from palm oil plantations alone is 100 million tonnes/year by 2020 (Malek et al., 2017), while the production of rice husk is 0.44 million tonnes/year. Bioethanol production via a second generation biofuel is also expected to be economically preferable in the future due to low feedstock cost. Lignocelluloses from agricultural, industrial and forest residuals consist of lignin, cellulose, hemicelluloses, and various other extractives. It contains both cellulose and hemicellulose that can be converted to ethanol by hydrolysis and fermentation. Glucose 6 58 VOL VOL 75 55 JULY-SEPTEMBER JUNE 2013 2018 (hexose sugar) and xylose (pentose sugar) are hydrolysed from cellulose and hemicellulose, respectively. The fermentation process would only be economically viable if both hexose and pentose sugars present in the lignocellulosic hydrolysates are converted to ethanol. The conventional Baker’s yeast, Saccharomyces cerevisiae can only uptake glucose and ferment it to ethanol, leaving behind the precious xylose. To achieve this, a micro-organism capable of utilising both glucose and xylose is very much anticipated. To add to the cost of operation, the addition of enzymes is needed to hydrolyse the lignocellulose into sugars during pre-treatment. This is where powerful genetic engineering tools may be applied to produce a super microbe, functioning as a factory that can cater to the full range of hydrolysis including broad range sugar consumption, ethanol production and, in addition, has the ability to handle fermentation stresses. Consolidated Bioethanol Processing Approach Conventional ethanol production involves separate hydrolysis and saccharification. Simultaneous saccharification and fermentation