Pretreatment optimisation of Ulva spp. for production of bioH2 and lactic acid as added-value product

Abstract

This study compares hydrothermal and diluted acid-thermal pretreatments at 100 °C for hydrolysate production from Ulva spp. Aiming at bioH2 production at 55 °C. Three extractants were evaluated in hydrothermal pretreatment: distilled water (H-DW), natural (H-NS) and synthetic seawater (H-SS). The HCl concentration (N), the Ulva spp. Percentage (% w/v), and hydrolysis time (h) in diluted acid-thermal pretreatment were optimised using a central composite design and a desirability function to maximise the total carbohydrate concentration and yield while minimising the HMF and furfural concentration. The hydrolysate from hydrothermal pretreatments, depending on the pretreatment time and %Ulva, achieved bioH2 production from 20 to 47% lower than the optimised diluted acid-thermal pretreatment (0.3 N HCl, 35%Ulva, and 2.5 h), which was 66.83 (±3.89) NmL gglucose−1. The hydrolysate also indicates potential for lactic acid (HLa) production, resulting in 1.47 molHLa molglucose−1, before being consumed after 1.6 days and contributing to the bioH2 production.