Integrated alkali pretreatment and preservation of wet lettuce (Pistia stratiotes) by lactic acid bacteria for fermentable sugar production

An integrated process was proposed by applying NaOH at high solid condition followed by ensilage to pretreat and preserve the biomass of water lettuce for fermentable sugar production. The results showed that the pretreatment with sodium hydroxide prior the inoculation of lactic acid bacteria effectively removed the lignin content from biomass of water lettuce and increased the extractable portion of the biomass. Experimental sets that had received alkali pretreatment had more total organic acids and fewer butyric acids generated than non-pretreated sets. The results also showed that the integrated process can preserve more carbohydrate content of biomass and can give higher fermentable sugar yields than without pretreatment. Overall, the study suggests that treatment with NaOH improves preservation of fresh harvested water lettuce but further investigation of optimal conditions is needed.