Bacterial cellulose (BC) has attracted attention as a new functional material due to its excellent mechanical strength, tridimensional nanostructure, high purity, and increased water absorption, compared to plant cellulose. In this work, commercial laccase was immobilized on BC and the influence of enzyme concentration, contact time, and pH was optimized toward the recovery activity of immobilized laccase. This optimization was carried out using a 33 experimental design and response surface methodology. Enzyme concentration played a critical role in laccase immobilization. Under optimized conditions (0.15 μL L−1 of enzyme concentration, 4.8 h of contact time, pH 5.4), the predicted and experimental response were equal to 47.88 and 49.30%, respectively. The thermal stability of the immobilized laccase was found to increase notably at 60 and 70°C presenting stabilization factor equal to 1.79 and 2.11, respectively. The immobilized laccase showed high operational stability, since it retained 86% of its initial activity after seven consecutive biocatalytic cycles of reaction with 2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid). Kinetic studies showed that the values of Michaelis–Menten constant and maximum reaction rate decreased upon immobilization (9.9‐ and 1.6‐fold, respectively). Globally, the use of immobilized laccase on BC offers an interesting tool for industrial biocatalytic applications.

The use of syngas, which can be sustainably derived from CO 2 or from exhaust gases of steel mills, is gaining increasing interest for the synthesis of added-value products. In this review, the state of the art and technological challenges emerging from the use of this gaseous feedstock are described. In addition, the possibility of converting syngas into methanol and its subsequent use as the substrate in a microbial fermentation stage are discussed.

In this work, we describe the construction of a synthetic metabolic pathway enabling direct biosynthesis of 1,3-propanediol (PDO) from glucose via the Krebs cycle intermediate malate. This non-natural pathway extends a previously published synthetic pathway for the synthesis of (L)-2,4-dihydroxybutyrate (L-DHB) from malate by three additional reaction steps catalyzed respectively, by a DHB dehydrogenase, a 2-keto-4-hydroxybutyrate (OHB) dehydrogenase and a PDO oxidoreductase. Screening and structure-guided protein engineering provided a (L)-DHB dehydrogenase from the membrane-associated (L)-lactate dehydrogenase of E . coli and OHB decarboxylase variants derived from the branched-chain keto-acid decarboxylase encoded by kdcA from Lactococcus lactis or pyruvate decarboxylase from Zymomonas mobilis . The simultaneous overexpression of the genes encoding these enzymes together with the endogenous ydhD -encoded aldehyde reductase enabled PDO biosynthesis from (L)-DHB. While the simultaneous expression of the six enzymatic activities in a single engineered E . coli strain resulted in a low production of 0.1 mM PDO from 110 mM glucose, a 40-fold increased PDO titer was obtained by co-cultivation of an E . coli strain expressing the malate-DHB pathway with another strain harboring the DHB-to-PDO pathway.