Abstract
Effective lactic acid (LA) production from lignocellulosic biomass materials is challenged by several limitations related to pentose sugar utilization, inhibitory compounds, and/or fermentation conditions. In this study, a newly isolated Bacillus coagulans strain Azu-10 was obtained and showed homofermentative LA production from xylose with optimal fermentation conditions at 50 °C and pH 7.0. Growth of strain Azu-10 and LA-fermentation efficiency were evaluated in the presence of various lignocellulose-derived inhibitors (furans, carboxylic acids, and phenols) at different concentrations. Furanic lignocellulosic-derived inhibitors were completely detoxified. The strain has exhibited high biomass, complete xylose consumption, and high LA production in the presence of 1.0–4.0 g/L furfural and 1.0–5.0 g/L of hydroxymethyl furfural, separately. Moreover, strain Azu-10 exhibited high LA production in the presence of 5.0–15.0 g/L acetic acid, 5.0 g/L of formic acid, and up to 7.0 g/L of levulinic acid, separately. Besides, for phenolic compounds, p-coumaric acid was most toxic at 1.0 g/L, while syringaldehyde or p-hydroxybenzaldehyde, and vanillin at 1.0 g/L did not inhibit LA fermentation. The present study provides an interesting potential candidate for the thermophilic LA fermentation from lignocellulose-derived substrates at the industrial biorefinery level.
Highlights
Lactic acid (LA) is a chemical compound with various industrial applications; besides, it can be used as a monomer for poly-lactic acid that is a biodegradable material alternative to petrochemical plastics
The LA yield (g/g) based on consumed sugars is calculated as the ratio of LA (g/L) to sugar xylose (g/L), LA productivity (g/(L·h)) is defined as the ratio of lactic acid concentration (g/L) to the fermentation time (h), and maximum LA productivity (g/(L·h)) was determined by the difference between LA concentrations of two respective samples divided by the time difference
Based on the isolation protocol, 14 isolates were obtained from different soil samples
Summary
Lactic acid (LA) is a chemical compound with various industrial applications; besides, it can be used as a monomer for poly-lactic acid that is a biodegradable material alternative to petrochemical plastics. Lignocellulosic feedstock for LA production by microbial fermentation has recently gained much interest due to its abundance, sustainability, avoidance of food crops’ utilization, environmental impact, and cost-effectiveness production process [2]. This material mainly consists of cellulose, hemicellulose, and lignin. Obtaining fermentable sugars from such biomass usually requires pretreatments by physical or chemical methods for delignification and isolation of cellulose fraction
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