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Significance This report describes an opportunity for the bacterial cellulose nanofiber (BCNF) membrane, which has recently been attracting much attention due to its sustainability and high thermal stability, as a “single-layer,” good alternative membrane to the existing chemical-derived one in batteries, and thus allows us to find possible solutions to the environmental and safety issues. We achieved highest BCNF yield ever reported so far and fabricated a cylindrical lithium ion battery (LIB) by roll-to-roll process to realize remarkable cycle stability with 80% capacity retention even after 1,000 cycles, which is comparable to those of commercialized batteries. Finally, we introduced a Lewis base to improve thermal safety of the battery to a level comparable to that of a commercial ceramic-coated separator.

Succinic acid was produced by continuous fermentation of Actinobacillus succinogenes sp. 130Z in an external membrane cell recycle reactor to improve viable cell concentration and productivity. Using this system, cell concentration increased to 16.4 g/l at the dilution rate 0.2 h-1, up to 3 times higher than that of batch culture, and the volumetric productivity of succinic acid increased up to 6.63 g/l/h at the dilution rate 0.5 h-1, 5 times higher than that of batch fermentation. However, in the continuous culture using a high dilution rate, operational problems including severe membrane fouling and contamination by lactic acid producer were observed. Another succinic acid producer, Mannheimia succiniciproducens MBEL55E, was also utilized in this system, and the cell concentration and productivity of succinic acid at the dilution rate of 0.3 h-1 were found to be above 3 and 2.3 times higher, respectively, compared with those obtained at the dilution rate of 0.1 h-1. These observations give a deep insight into the process design for a continuous succinic acid production by microorganisms.

Volatile fatty acids (VFAs) derived from organic waste, were used as a low cost carbon source for high bioreactor productivity and titer. A multi-stage continuous high cell density culture (MSC-HCDC) process was employed for economic assessment of microbial lipids for biodiesel production. In a simulation study we used a lipid yield of 0.3 g/g-VFAs, cell mass yield of 0.5 g/g-glucose or wood hydrolyzates, and employed process variables including lipid contents from 10–90% of cell mass, bioreactor productivity of 0.5–48 g/L/h, and plant capacity of 20000–1000000 metric ton (MT)/year. A production cost of USD 1.048/kg-lipid was predicted with raw material costs of USD 0.2/kg for wood hydrolyzates and USD 0.15/kg for VFAs; 9 g/L/h bioreactor productivity; 100, 000 MT/year production capacity; and 75% lipids content. The variables having the highest impact on microbial lipid production costs were the cost of VFAs and lipid yield, followed by lipid content, fermenter cost, and lipid productivity. The cost of raw materials accounted for 66.25% of total operating costs. This study shows that biodiesel from microbial lipids has the potential to become competitive with diesels from other sources.

Dissolved oxygen (DO)-controlled nar promoter expression vectors were constructed, and their expression efficiency was compared with that of the T7 promoter pET22 expression vector by expressing human growth hormone (hGH), enhanced green fluorescence protein (EGFP), and β-tyrosinase in Escherichia coli cells. The nar promoter expression vector pRBS, which was engineered with a 5′-untranslated region and ribosomal binding site for the T7 promoter, expressed hGH at a rate of up to 32% of the total cellular proteins (TCP) in E. coli W3110narL − . The expression level of hGH was further enhanced, up to ∼42% of the TCP, by adding the N-terminal peptide tag of β-galactosidase to hGH, which was comparable to the expression of ∼43% of the TCP in pET-lac:hGH/BL21(DE3). A further engineered expression vector, pRBS(fnr), which coexpressed fumarate/nitrate reductase ( fnr ), expressed more EGFP than pET22 in BL21(DE3). In addition, recombinant β-tyrosinase was successfully expressed at a rate of up to ∼45% of the TCP in pRBS(fnr) in W3110narL − . From these results, the DO-controlled nar promoter system developed in this study can be considered a reliable and cost-effective expression system for protein production, especially in large-scale fermentation, as an alternative to the pET/BL(DE3) system.