Homoethanol production from cellobionate and glycerol using recombinant Klebsiella oxytoca strains

Cellobionate production from sodium hydroxide pretreated wheat straw by engineered Neurospora crassa HL10

This study investigated cellobionate production from a lignocellulosic substrate using Neurospora crassa HL10. Utilizing NaOH-pretreated wheat straw as the substrate obviated the need for an exogenous redox mediator addition, as lignin contained in the pretreated wheat served as a natural mediator. The low laccase production by N. crassa HL10 on pretreated wheat straw caused slow cellobionate production, and exogenous laccase addition accelerated the process. Cycloheximide induced substantial laccase production in N. crassa HL10, enabling the strain to yield approximately 57 mM cellobionate from pretreated wheat straw (equivalent to 20 g/L cellulose), shortening the conversion time from 8 to 6 days. About 92% of the cellulose contained in the pretreated wheat straw is converted to cellobionate. In contrast to existing methods requiring pure cellobiose or cellulase enzymes, this process efficiently converts a low-cost feedstock into cellobionate at a high yield without enzyme or redox mediator supplementation.

Bioproduction and applications of aldobionic acids with a focus on maltobionic and cellobionic acid

Aldobionic acids are sugar acids which consist of a disaccharide with an anomeric acid group. The most famous is lactobionic acid (LBA). LBA is used in many applications such as food and beverages, pharmaceuticals and medicine, cosmetics or chemical processes. During the last decade, all these industries are observing a shift of consumer preferences towards plant-based options. Thus, the biotechnological industry is trying to replace the animal-derived LBA. Maltobionic acid (MBA) and cellobionic acid (CBA) are two stereoisomers of LBA which have emerged as vegan alternatives. However, MBA and CBA face different obstacles related to their industrial production. While traditionally used electrochemical or chemical catalysis often rely on cost intensive and/or hazardous catalysts, novel production methods with microorganisms are still poorly studied. In the first part, this paper discusses both alternatives in terms of their characteristics and applications. In the second part, it reviews the long-studied chemical production and the novel bioproduction methods, which are based on enzymatic and microbial systems. This review concludes with a discussion of future work needed to bring their production to the industrial scale.

Genome, metabolic pathways and characteristics of cometabolism of dibenzothiophene and the biodiesel byproduct glycerol in Paraburkholderia sp. C3

Utilization of glycerol, a biodiesel byproduct, has not been well explored. In the present study, glycerol and the other carbon sources were studied for cometabolism of dibenzothiophene (DBT), a model chemical commonly used in bioremediation studies, by Paraburkholderia sp. C3. This study showed a direct association between rhamnolipids (RLs) biosynthesis and DBT biodegradation induced by different carbon sources in a Paraburkholderia specie. Glycerol can induce the strain C3 produce at least four RLs. The RL precursor is mainly derived from the fatty acid synthesis (FAS II) and β-oxidation pathway. The genome contained two (fabF and fabG) and four (fadA, fadE, fadB and echA) genes involved in FAS II and β-oxidation, respectively. The genome also carried the rhlA and rhlB genes involved in rhamnosyltransferase for RL biosynthesis and two DBT dioxygenase genes (nahAc and catA). The findings suggest a viable approach of using the biodiesel byproduct glycerol to remediate contaminated environments.