Transformation and electrophoretic karyotyping of Coniochaeta ligniaria NRRL30616

Effect of lignin-blocking agent on enzyme hydrolysis of acid pretreated hemp waste

Hemp wastes (stems and branches), fractionated after hemp flower extraction for the production of cannabidiol oil, were utilized as a potentially renewable resource for the sugar flatform process. Hydrolysis of cellulose from the acid pretreated hemp biomass using a commercial enzyme was tested and evaluated for its chemical composition, morphological change, and sugar recovery. Acid pretreated hemp stems and branches, containing 1% glucan (w/v) solids, were hydrolyzed for 72 h using 25 mg enzyme protein per g glucan. A 54% glucose conversion was achieved from the treated branches versus a 71% yield from the treated stems. Raw branches and stems yielded 35% and 38% glucose, respectively. Further tests with a lignin-blocking additive (e.g. bovine serum albumin) resulted in a 72% glucose yield increase for stem hydrolysis using 10 mg enzyme protein per g glucan. While pretreatment promotes amorphous hemicellulose decrease and cellulose decomposition, it causes enzyme inhibition/deactivation due to potential inhibitors (phenols and lignin-derived compounds). This study confirms the addition of non-catalytic proteins enhances the cellulose conversion by avoiding non-productive binding of enzymes to the lignin and lignin-derived molecules, with lignin content determining the degree of inhibition and conversion efficiency.

Genetic transformation of Coniochaeta sp. 2T2.1, key fungal member of a lignocellulose-degrading microbial consortium

Coniochaeta sp. strain 2T2.1 is a key member of a microbial consortium that degrades lignocellulosic biomass. Due to its ecological niche and ability to also grow in pure culture on wheat straw, protocols for transformation and antibiotic selection of the strain were established. Hygromycin was found to be a reliable selectable transformation marker, and the mammalian codon-optimized green fluorescent protein was expressed and used to visualize fluorescence in transformed cells of strain 2T2.1.

Use of green fluorescent protein to monitor fungal growth in biomass hydrolysate

A reporter gene encoding green fluorescent protein (GFP) was introduced into the ascomycete Coniochaeta ligniaria NRRL30616, and fluorescence of cultures was monitored as a measure of cell growth. Fluorescence in the GFP-expressing strain was measured during growth of cells in defined and complex media as well as in the liquor derived from pretreatment of corn stover, an agricultural residue. Fluorescence mirrored growth of cultures, as measured by optical density and counts of colony forming units. Because traditional methods to monitor growth cannot be used in biomass liquors due to its fibrous, dark-colored nature, the speed and convenience of using GFP to monitor growth is advantageous. Fluorescence of cultures in biomass hydrolysate also correlated with the concentration of furfural in hydrolysate. Furfural and other compounds, present in hydrolysate due to physico-chemical pretreatment of biomass, are inhibitory to fermenting microbes. Therefore, measurement of fluorescence in GFP-expressing C. ligniaria is a proxy for measures of microbial growth and furfural consumption, and serves as a convenient indicator of metabolism of fermentation inhibitors in biomass hydrolysate.