Extending galactose-oxidation pathway of Pseudomonas putida for utilization of galactose-rich red macroalgae as sustainable feedstock.

Marine red macroalgae has attracted researchers' consideration as a non-lignocellulosic feedstock for microbial growth to produce biofuels and biochemical products. Gelidium amansii is representative galactose-rich red macroalgae biomass but studies on its galactose utilization are currently scarce. Herein, we engineered Pseudomonas putida KT2440 as a functional chassis for assimilation of galactose in addition to glucose in G. amansii hydrolysate. P. putida KT2440 was confirmed owning high ability to oxidize galactose to galactonate by glucose dehydrogenase. Thereafter galactose-oxidation pathway was extended by introducing galactonate transport and metabolism modules from Pseudomonas rhodesiae NL2019. The recombinant strains NL910 and NL911 were able to grow on galactose with high cell densities and growth rates, and simultaneously upgrade all red macroalgae streams, which is essential to develop a sustainable and cost-effective bioprocess for valorization of red macroalgae.

A comprehensive review on microbial production of 1,2-propanediol: micro-organisms, metabolic pathways, and metabolic engineering.

1,2-Propanediol is an important building block as a component used in the manufacture of unsaturated polyester resin, antifreeze, biofuel, nonionic detergent, etc. Commercial production of 1,2-propanediol through microbial biosynthesis is limited by low efficiency, and chemical production of 1,2-propanediol requires petrochemically derived routes involving wasteful power consumption and high pollution emissions. With the development of various strategies based on metabolic engineering, a series of obstacles are expected to be overcome. This review provides an extensive overview of the progress in the microbial production of 1,2-propanediol, particularly the different micro-organisms used for 1,2-propanediol biosynthesis and microbial production pathways. In addition, outstanding challenges associated with microbial biosynthesis and feasible metabolic engineering strategies, as well as perspectives on the future microbial production of 1,2-propanediol, are discussed.

Comprehensive utilization of corncob for furfuryl alcohol production by chemo-enzymatic sequential catalysis in a biphasic system.

A new process for the production of furfuryl alcohol from corncob was constructed by using deep eutectic solvents and whole cell catalysis in this paper. Firstly, the corncob was treated with deep eutectic solvents to convert the xylan into furfural, and then the pretreated corncob residue was enzymatically hydrolyzed to obtain a glucose-rich enzymatic hydrolysate, which was used to provide NADH for Bacillus coagulans NL01 during the process of furfural reduction. The furfural yield could reach 46% using the selected choline chloride-oxalic acid as catalysts and corncob as substrate under the optimized catalytic condition at 120 °C for 30 min. The final furfuryl alcohol yield of 20.7% was achieved with corncob as substrate. Moreover, this catalytic system realized the recycling of deep eutectic solvents three times, the high-value production of furfuryl alcohol, and the comprehensive utilization of corncob.

One-pot biosynthesis of furfuryl alcohol and lactic acid via a glucose coupled biphasic system using single Bacillus coagulans NL01.

Furfuryl alcohol is an important reduction product from biomass derived furfural. This study developed one-pot biosynthesis of furfuryl alcohol and lactic acid by a glucose coupled biphasic system using single Bacillus coagulans NL01. Water/dioctyl phthalate is chosen as biphasic system to alleviate the toxicity of furfural and furfuryl alcohol. Under the optimal conditions, the high-concentration conversion (208 mM) of furfural was successfully converted in 6 h reaction with 98% furfural conversion and 88% furfuryl alcohol selectivity. Notably, glucose as co-substrate could be effectively converted to lactic acid in this biphasic system. About 264 mM furfuryl alcohol and 64.2 g/L lactic acid were simultaneously produced from 310 mM furfural and 71.3 g/L glucose within 8.5 h by a fed-batch strategy. The developed approach can not only increase the produced furfuryl alcohol concentration but also reduce the cost of overall approach by lactic acid co-production, indicating its potential for industrial applications.