抄録
To achieve regional growth in addition to mitigation of global warming and development of a recycling-based society, we are developing systems for advanced utilization of rural biomass resources, such as non-edible portions of agricultural products and food wastes.
Here, we introduce our sugar and enzyme production systems for practical use of rural cellulosic resources on a small scale in regional areas.
1) For sugar production from regional feedstocks, we constructed a very simple process, ‘CaCCO (Calcium Capturing by carbonation (CO2)) process’ which is based on Ca(OH)2-pretreatment. In this process, after the pretreatment step Ca(OH)2 is neutralized by carbonation to precipitate the Ca ion as CaCO3, which remained in the vessel during the subsequent enzymatic hydrolysis. The CaCCO process does not require a solid-liquid-separation step, and thus represents a novel pretreatment method to utilize not only cellulose but also xylan, starch, and sucrose in biomass. Furthermore, we proposed an improved CaCCO process that could reduce energy and water consumption and preserve feedstocks consistently. These simple processes would allow us to produce cost-effective and economically-friendly sugars on a small scale in rural areas.
2) For enzyme production from regional biomass, we developed an efficient production system of the saccharification enzymes for cellulosic materials, via continuously fed cultivation of glucose-depressed Trichoderma reesei mutants using soluble sugars. In this system, only soluble sugars are used as main carbon source(s) and enzyme inducers. The composition of enzymes produced from the mutants could be readily optimized by controlling the components of sugars and the pattern of addition, facilitating tailored production of enzymes in response to a diversity of feedstocks and conversion processes. We also found that relatively inexpensive sugars like the hydrolysate of cellulosic materials, starch and sucrose can be applied in this system. Furthermore, the semi-continuous cultivation, defined as continuously fed cultivation with managing culture fluid volume, allowed us to produce quality/quantity-controlled enzymes consistently and for the long term.
