Bioethanol and lipid production from the enzymatic hydrolysate of wheat straw after furfural extraction

Abstract

This study investigates biofuel production from wheat straw hydrolysate, from which furfural was extracted using a patented method developed at the Latvian State Institute of Wood Chemistry. The solid remainder after furfural extraction, corresponding to 67.6% of the wheat straw dry matter, contained 69.9% cellulose of which 4% was decomposed during the furfural extraction and 26.3% lignin. Enzymatic hydrolysis released 44% of the glucose monomers in the cellulose. The resulting hydrolysate contained mainly glucose and very little amount of acetic acid. Xylose was not detectable. Consequently, the undiluted hydrolysate did not inhibit growth of yeast strains belonging to Saccharomyces cerevisiae, Lipomyces starkeyi, and Rhodotorula babjevae. In the fermentations, average final ethanol concentrations of 23.85 g/l were obtained, corresponding to a yield of 0.53 g ethanol per g released glucose. L. starkeyi generated lipids with a rate of 0.08 g/h and a yield of 0.09 g per g consumed glucose. R. babjevae produced lipids with a rate of 0.18 g/h and a yield of 0.17 per g consumed glucose. In both yeasts, desaturation increased during cultivation. Remarkably, the R. babjevae strain used in this study produced considerable amounts of heptadecenoic, α,- and γ-linolenic acid.

Oleaginous yeast as a component in fish feed

“…We have recently demonstrated that the oleaginous yeast Lipomyces starkeyi can efficiently synthesise lipids from the hemicellulose fraction of birch wood and the cellulose fraction of wheat straw 19 , 20 , and other studies have also used lignocellulose hydrolysate as a substrate for oil production with this yeast 21 – 24 . The lipid composition of L. starkeyi was shown to be similar to that of saturated fatty acids (SFA) rich VO, for example olive oil or palm oil 19 , 20 , 25 . In this pilot study, the aim was to test whether it is possible to replace VO in the feed for Arctic char ( Salvelinus alpinus ) with single cell oils derived from L. starkeyi grown on lignocellulose hydrolysate from wheat straw, i.e .…”

Direct Saccharification and Fermentation for High Glucose and Ethanol Production from Non‐Detoxified Furfural Residue Without Any Pretreatment

“…Furfural residue (FR), a major waste byproduct during commercial furfural production process, is a valuable biomass resource. As reported, the global annual furfural production was around 300, 000 t at 2010, and the global furfural market is expected to reach 650, 000 t at 2020 . China, one of the largest furfural producers and exporters in the world, produces at least 200, 000 t furfural annually .…”

Biofuel production from straw hydrolysates: current achievements and perspectives

“…There are, however, large variation in the proportions of the three major polymers in straw. In some studies, cellulose contents of wheat straw were found to reach almost 50% (Brandenburg et al 2018 ; Saha et al 2005 ). This composition variation is apparently due to differing proportions of tissues in different cultivars, i.e.…”

“…Fermentation inhibitors are formed as side products of physico-thermal pretreatment. Under acid pretreatment, sugar dehydration results in the formation of 2-furaldehyde (furfural) from pentoses and hydroxymethyl furfural (HMF) from hexoses (Brandenburg et al 2018 ; Jönsson and Martín 2016 ). At severe pretreatment conditions, furaldehydes are further degraded to levulinic and formic acids.…”

“…Pentoses were in principle completely converted to furfural, and the hydrolysate contained the easily fermentable glucose. Moreover, the hydrolysate had a low content of fermentation inhibitors (Brandenburg et al 2018 ). It is also possible to utilise the lipids of oleaginous yeasts for other purposes, for instance as ingredient in fish feed, to replace vegetable oil such as palm oil.…”