(741c) Integrated Pretreatment and Wet Storage of Water Lettuce (Pistia stratiotes) and Sea Lettuce (Ulva lactuca) for Biofuel Production

Aquatic plant biomasses have been proposed to be potential feedstocks for biofuel production. However, the high moisture content makes the storage of fresh aquatic plant biomasses a challenge. Wet storage with the aid of microorganism possesses many advantages over dry storage including low risk of fire and less loss of dry matter.  In this study, an integrated system was developed by applying alkali or enzymatic pretreatment and Lactobacillus plantarum BCRC 10069 to the wet storage of water lettuce and sea lettuce which were harvested from local wastewater treatment facility and seashore respectively.  Full factorial experiments were designed to investigate the effects of loading of pretreatment agents, pretreatment time and post-pretreatment handling processes on the wet storage quality for a 28 day period.  The results showed that the pretreatment at high solid content prior the inoculation of L. plantarum effectively removed the lignin content from biomass of water lettuce and increase the amount of free sugars in both types of aquatic biomasses.  The free sugars especially glucose were consumed and organic acids were produced during the wet storage period.  Experimental sets received pretreatment also had more pH value drop than non-pretreated sets but a slightly higher loss of dry matter durig wet storage stage. Enzymatic digestibility of wet-stored biomasses and the fermentability of enzymatic hydrolysate to bioethanol and microbial oil were investigated as well.