Exploring optimal strategies for aquatic macrophyte pre-treatment: Sustainable feedstock for biohydrogen production. (September 2020)

• Record Type: Journal Article
• Authors: Karthikeya, K.; Sarma, Mrinal Kumar; Ramkumar, N.; Subudhi, Sanjukta
• Is Part Of: Biomass and bioenergy. Volume 140(2020)
• Publication Date: 2020-09
• Subjects: Eichhornia crassipes -- Azolla microphylla -- Dilute acid pre-treatment -- Factorial approach -- C5 & C6 fermentable sugar -- Biohydrogen -- Dark fermentation; Biomass energy -- Periodicals; Biomass -- Periodicals; Energy-Generating Resources -- Periodicals; Bioénergie -- Périodiques; 333.9539
• DOI: 10.1016/j.biombioe.2020.105678
• Languages: English
• ISSNs: 0961-9534

Abstract

Abstract: Aquatic macrophytes; Water hyacinth ( Eichhornia crassipes ) and Azolla, biomass have certain advantages over terrestrial plant biomass to use as non-edible feed for 2 nd generation bioenergy production. This is mainly due to the lower lignin content and higher productivity of aquatic macrophytes. These macrophytes do not require arable land. Present study explored on development of factorial approach based optimal pretreatment process for mild acid hydrolysis of Eichhornia crassipes and Azolla microphylla biomass for conversion to fermentable sugars. The simpler structure of aquatic plants translates to higher sugar recovery using milder pretreatment conditions compared to terrestrial plants. H2 SO4 & HCl used in mild concentrations for acid hydrolysis experiments. Approximately, 20% of the dry biomass was recovered as fermentable sugar (mainly xylose) upon treatment with dilute sulphuric acid (0.5–1.5% v/v) or hydrochloric acid (2–4% v/v) at 100–120 °C for 30–60 min. Within this range of parameters, sugar yield followed a simple additive model, implying that a decrease in sugar yield is due to reduction of one parameter. This provides a choice between high temperature short time (HTST) and low temperature long time (LTLT) treatments. HTST requires sophisticated pressure vessels and correspondingly higher capital investment for the advantage of a higher throughput. LTLT treatments can be performed in cost economy manner using relatively simple equipment. For economic, environmental and technical reasons, acid addition should be kept to a minimum, which is possible by a choice of higher temperature and longer treatment time. Such pretreatment may be employed as the first step of a two-step pretreatment process prior to enzymatic saccharification of cellulosic fraction. The acid pre-treated hydrolysate of water hyacinth and Azolla microphylla explored for hydrogen production through dark fermentation process through employment of C5 & C6 sugar utilizing microbe Enterobacter cloacae DT-1 strain. Highlights: Pretreatment (PT) with dilute HCl enhances sugar yield in water hyacinth. Pretreatment (PT) of Azolla microphylla biomass with dilute HCl and H2 SO4 gave similar sugar yield. High Temperature in PT enhances conversion of polysaccharides to simple sugars. Acid concentration influences the quantity of fermentable sugar yield. E. cloacae DT-1 strain produces H2 from Azolla and water hyacinth biomass sugars.