RESUMEN
The use of additives in the enzymatic saccharification of lignocellulosic biomass can have positive effects, decreasing the unproductive adsorption of cellulases on lignin and reducing the loss of enzyme activity. Soybean protein stands out as a potential lignin-blocking additive, but the economic impact of its use has not previously been investigated. Here, a systematic evaluation was performed of the process conditions, together with a techno-economic analysis, for the use of soybean protein in the saccharification of hydrothermally pretreated sugarcane bagasse in the context of an integrated 1G-2G ethanol biorefinery. Statistical experimental design methodology was firstly applied as a tool to select the process variable solids loading at 15% (w/w) and soybean protein concentration at 12% (w/w), followed by determination of enzyme dosage at 10 FPU/g and hydrolysis time of 24 h. The saccharification of sugarcane bagasse under these conditions enabled an increase of 26% in the amount of glucose released, compared to the control without additive. The retro-techno-economic analysis (RTEA) technique showed that to make the biorefinery economically feasible, some performance targets should be reached experimentally such as increasing biomass conversion to ideally 80% and reducing enzyme loading to 5.6 FPU/g in the presence of low-cost soybean protein.
Asunto(s)
Saccharum/metabolismo , Proteínas de Soja/metabolismo , Biomasa , Celulosa/metabolismo , Glycine max/metabolismoRESUMEN
A potential strategy to mitigate problems related to unproductive adsorption of enzymes onto lignin during the saccharification of lignocellulosic biomass is the addition of lignin-blocking agents to the hydrolysis reaction medium. However, there is a clear need to find more cost-effective additives for use in large-scale processes. Here, selected alternative low-cost additives were evaluated in the saccharification of steam-exploded sugarcane bagasse using a commercial enzymatic cocktail. The addition of soybean protein, tryptone, peptone, and maize zein had positive effects on glucose release during the hydrolysis, with gains of up to 36% when 8% (w/w) soybean protein was used. These improvements were superior to those obtained using bovine serum albumin (BSA), a much more expensive protein that has been widely reported for such an application. Moreover, addition of soybean protein led to a saving of 48 h in the hydrolysis, corresponding to a 66% decrease in the reactor operation time required. In order to achieve the same hydrolysis yield without the soybean additive, the enzyme loading would need to be increased by 50%. FTIR spectroscopy and nitrogen elemental analysis revealed that the additives probably acted to reduce unproductive binding of cellulolytic enzymes onto the lignin portion of the sugarcane bagasse.