Detoxification of water hyacinth hydrolysate mediated by exopolysaccharide-based hydrogel enhances hydrogen and methane production.

In this study, the exopolysaccharide from cyanobacteria was used for detoxification of acid hydrolysate of water hyacinth biomass. Exopolysaccharide-hydrogel showed phenolics and furans removal of 86 % and 97 %, respectively, with sugar recovery of 98.3 %. The fermentation of detoxified acid hydrolysate was integrated with that of pretreated biomass subjected to enzymatic saccharification derived from commercial cellulose (ESF) or from microbe (MSF). The maximum hydrogen production of 69.2 mL/g-VS was obtained in MSF, which is 1.2- and 1.6-fold higher than ESF and undetoxified acid hydrolysate, respectively. Additionally, the methane production of 12.6 mL/g-VS by mixed methanogenic consortia was obtained using the spent liquor containing volatile fatty acids. This enhanced hydrogen and methane production in subsequent microbial processes is mainly attributed to the selective removal of inhibitors in combination with an integrated carbohydrate utilization.

Xylitol bioproduction: state-of-the-art, industrial paradigm shift, and opportunities for integrated biorefineries.

Recent advances in biomass conversion technologies have shown a promising future toward fermentation during xylitol production. Xylitol is one of the top 12 renewable added-value chemicals that can be obtained from biomass according to US Department of Energy (USDOE). Currently, xylitol accounts for approximately US$823.6 million of annual sales in the market, and this amount is expected to reach US$1.37 billion by 2025. This high demand has been achieved owing to the chemical conversion of hemicellulosic hydrolysates from different lignocellulosic biomasses, which is a costly and non-ecofriendly process. Xylose-rich hemicellulosic hydrolysates are the major raw materials for xylitol production through either chemical or biotechnological routes. Economic production of a clean hemicellulosic hydrolysate is one of the major bottlenecks for xylitol production on the commercial scale. Advancements in biotechnology, such as the isolation of novel microorganisms, genetic manipulation of xylose metabolizing strains, and modifications in the fermentation process, can enhance the economic feasibility of xylitol production on the large scale. Furthermore, xylitol production in integrated biorefineries can be even more economic, given the readily available raw materials and the co-use of steam, electricity, and water, among others. Exploring new biotechnology techniques in integrated biorefineries would open new markets and opportunities for sustainable xylitol production to fulfill the market's growing demands for this sugar alcohol. This article is a review of the advancements reported in the whole biotechnological process for xylitol production, and involve pretreatment technologies, hemicellulosic hydrolysate preparation, xylose conversion into xylitol, and product recovery. Special attention is devoted to current metabolic engineering strategies to improve this bioprocess, as well as to the importance of xylitol production processes in biorefineries.

Bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification, and ethanol fermentation.

Depleted supplies of fossil fuel, regular price hikes of gasoline, and environmental damage have necessitated the search for economic and eco-benign alternative of gasoline. Ethanol is produced from food/feed-based substrates (grains, sugars, and molasses), and its application as an energy source does not seem fit for long term due to the increasing fuel, food, feed, and other needs. These concerns have enforced to explore the alternative means of cost competitive and sustainable supply of biofuel. Sugarcane residues, sugarcane bagasse (SB), and straw (SS) could be the ideal feedstock for the second-generation (2G) ethanol production. These raw materials are rich in carbohydrates and renewable and do not compete with food/feed demands. However, the efficient bioconversion of SB/SS (efficient pretreatment technology, depolymerization of cellulose, and fermentation of released sugars) remains challenging to commercialize the cellulosic ethanol. Among the technological challenges, robust pretreatment and development of efficient bioconversion process (implicating suitable ethanol producing strains converting pentose and hexose sugars) have a key role to play. This paper aims to review the compositional profile of SB and SS, pretreatment methods of cane biomass, detoxification methods for the purification of hydrolysates, enzymatic hydrolysis, and the fermentation of released sugars for ethanol production.