Delignification and detoxification of peanut shell bio-waste using an extremely halophilic laccase from an Aquisalibacillus elongatus isolate

Abstract

Lignocellulose bioconversion is a harsh process requiring the use of surfactants and organic solvents. Consequently, the incorporation of laccases in this bioconversion requires the bioprospecting of enzymes that can remain stable under extreme conditions. An extracellular, highly stable laccase was produced by the halophilic isolate Aquisalibacillus elongatus in submerged liquid culture fermentation. Statistical and non-statistical strategies gave the highest enzymatic activity (8.02 U mL) following addition of glucose (1.7 g L), copper sulfate (0.8 g L), urea (15 g L), and CaCl (0.8 g L). The enzyme, after purification using a synthetic affinity support, delignified a peanut shell substrate by 45%. A pH of 8.0 and a temperature of 35 °C were optimal for delignification of this bio-waste material. Addition of [Bmim][PF], 1,4-dioxane, acetone, and HBT promoted this bio-waste delignification. Bio-treatment in the presence of 50% [Bmim][PF] gave a maximal lignin removal of 87%. The surfactants tested had no significant effects on the delignification yield. The laccase also detoxified the toxic phenols found in peanut shell waste. The high catalytic efficiency of this enzyme against a lignocellulosic sample under extreme conditions suggests the suitability of this laccase for industrial applications.

Characterization of the Microbial Population Inhabiting a Solar Saltern Pond of the Odiel Marshlands (SW Spain)

“…[ 56 ] and Natrialba magadii [ 57 ]. However, only few cellulases [ 58 , 59 , 60 ] and laccases [ 61 , 62 ] producing halophiles have been reported.…”

Lignin Valorization: Production of High Value-Added Compounds by Engineered Microorganisms

“…Halophiles bacteria are quite interesting due to the uncommon resistance to high saline levels, a feature usually linked to remarkable tolerance to UV light radiations, temperature, and extreme pH values. Actually, Penicillium chrysogenum, isolated in saline soil, has the capability to depolymerize lignin directly on olive milled substrate from oil production [48]; meanwhile, several halophilic ligninolytic enzymes were isolated and tested on raw substrates such as sugar beet pulp [49], almond shells [50] or peanut shells [51]. All these microorganisms, and related enzymes, were tested successfully on such substrates with minimal or no pre-treatment.…”

Recent Developments in the Delignification and Exploitation of Grass Lignocellulosic Biomass

“…158 Al-Zuhair et al investigated the enzymatic delignification of seaweed biomass (a mix of Chaetomorpha and Cladophora species), carried out using TvL, HBT, and [EMIM][OAc] obtaining a delignification degree up to 27%. 162 Rezaei et al reported the use of LC from the halophilic bacterium Aquisalibacillus elongatus in the presence of [BMIM]-[PF 6 ] (1-butyl-3-methylimidazolium hexafluorophosphate) to delignify sugar beet pulp, obtaining a delignification yield of 78.4% after 24 h. 163 The same enzyme was also tested in the same conditions in [BMIM][PF 6 ] to remove lignin from peanut shell, obtaining a lignin removal of 87% after 24 h. 164 Deep Eutectic Solvents. Deep eutectic solvents (DESs) are a new class of green solvents composed of a hydrogen bond acceptor (HBA, usually a quaternary ammonium salt) and a hydrogen bond donor (HBD) such as glycerol, succinic acid, etc.…”

“…Rezaei et al reported the use of LC from the halophilic bacterium Aquisalibacillus elongatus in the presence of [BMIM]­[PF 6 ] (1-butyl-3-methylimidazolium hexafluorophosphate) to delignify sugar beet pulp, obtaining a delignification yield of 78.4% after 24 h . The same enzyme was also tested in the same conditions in [BMIM]­[PF 6 ] to remove lignin from peanut shell, obtaining a lignin removal of 87% after 24 h …”