Insights into biological delignification of rice straw by Trametes hirsuta and Myrothecium roridum and comparison of saccharification yields with dilute acid pretreatment

Abstract

Rice straw is the most abundant agricultural residue on a global scale and is widely available as feedstock for cellulosic fuel production. However, it is highly recalcitrant to biochemical deconstruction and also generates inhibitors that affect enzymatic saccharification. Rice straw from eastern Arkansas was subjected to dilute acid pretreatment (160 °C, 48 min and 1.0 % sulfuric acid) and solid-state fermentation with two lignocellulolytic fungi, Trametes hirsuta and Myrothecium roridum, and their saccharification efficacies were compared. T. hirsuta and M. roridum were tested separately; pretreatment of rice straw with either strain for seven days resulted in 19 and 70 % enrichment of its holocellulose content, respectively. However, liquid chromatography analysis of the alkali extracts showed significant differences in cell wall degradation by T. hirsuta and M. roridum. T. hirsuta removed 15 % more phenolic compounds and 38 % more glucan than M. roridum, while M. roridum removed 77 % more xylan than T. hirsuta. Fungal and dilute acid pretreated biomass was then hydrolyzed using Accellerase® 1500, a saccharification cocktail. Saccharification efficiency of M. roridum was 37 % higher than that of dilute acid pretreatment of rice straw, requiring 8 % lower enzyme loading and 50 % shorter enzymatic hydrolysis duration. Alkali extraction of fungal pretreated biomass also yielded 10 to 15 g kg-1 of acid precipitable polymeric lignin (APPL), which is a valuable co-product for biorefineries. In comparison to dilute acid pretreatment, fungal pretreatment could be a cost-effective alternative for the degradation of recalcitrant biomass, such as rice straw.

Biological wheat straw valorization: Multicriteria optimization of Polyporus brumalis pretreatment in packed bed bioreactor

“…These different, complementary, and synergistic catalytic activities utilized by WR fungi at the right time constitute an efficient lignocellulose degradation mechanism. Many WR fungi have been studied for biological pretreatment of various lignocellulosic biomasses (Liu et al., ; Mohanram, Rajan, Carrier, Nain, & Arora, ; Vasco‐Correa & Li, ) allowing holocellulose enrichment with a high delignification of the biomass. Within fungal species and strains, this ability depends of course on feedstock nature, but it also depends on the SSF culture conditions.…”

High‐performance of Agaricus blazei fungus for the biological pretreatment of elephant grass

“…The saccharification of cellulose is shown as an interesting alternative for the disposal of agricultural and agroforestry waste. However, for the hydrolysis process to be efficient, it requires access to the enzymes present in the cellulose substrate …”

“…For the application of these methods, white and soft degradation fungi are used to degrade both cellulose and lignin, and brown degradation fungi are mainly used to degrade cellulose . However, white degradation fungi have received considerable attention due to their ability to selectively degrade lignin …”

Straw Degradation Behaviors under Different Conditions of Relative Air Humidity and Ultraviolet-A Irradiation

“…With a change in the quantity, activity, and functional diversity of the microbial community, obvious mass losses in lignocellulosic materials have been observed during biodegradation. A wide variety of enzyme systems are generated during microbial metabolism, which plays a crucial role in the degradation process (Wihan 2007;Buraimoh et al 2015;Mohanram et al 2015). Compared with the biodegradation of crop residue, which is mostly driven by straw-degrading microorganisms, the exact process of photodegradation has not been clearly expounded (Baker and Allison 2015).…”