Integrated butanol recovery for an advanced biofuel: current state and prospects

Butanol has recently gained increasing interest due to escalating prices in petroleum fuels and concerns on the energy crisis. However, the butanol production cost with conventional acetone–butanol–ethanol fermentation by Clostridium spp. was higher than that of petrochemical processes due to the low butanol titer, yield, and productivity in bioprocesses. In particular, a low butanol titer usually leads to an extremely high recovery cost. Conventional biobutanol recovery by distillation is an energy-intensive process, which has largely restricted the economic production of biobutanol. This article thus reviews the latest studies on butanol recovery techniques including gas stripping, liquid–liquid extraction, adsorption, and membrane-based techniques, which can be used for in situ recovery of inhibitory products to enhance butanol production. The productivity of the fermentation system is improved efficiently using the in situ recovery technology; however, the recovered butanol titer remains low due to the limitations from each one of these recovery technologies, especially when the feed butanol concentration is lower than 1 % (w/v). Therefore, several innovative multi-stage hybrid processes have been proposed and are discussed in this review. These hybrid processes including two-stage gas stripping and multi-stage pervaporation have high butanol selectivity, considerably higher energy and production efficiency, and should outperform the conventional processes using single separation step or method. The development of these new integrated processes will give a momentum for the sustainable production of industrial biobutanol.     

Heme oxygenase-1 silencing increases the sensitivity of human osteosarcoma MG63 cells to arsenic trioxide

Arsenic trioxide (ATO) has been successfully used to treat leukemia and some solid malignant tumors. Our previous study regarding the effects of ATO on mesenchymal-derived human osteosarcoma MG63 cells showed that heme oxygenase-1 (HO-1) was strongly induced upon treatment with ATO. The present study sought to investigate the effect of silencing HO-1 on the sensitivity of osteosarcoma cells to ATO to determine the potential for therapeutic applications. Small hairpin RNA (shRNA)-mediated interference was used to silence HO-1 in MG63 cells. Viability, apoptosis, and intracellular reactive oxygen species (ROS) of the cells were assessed to evaluate the sensitivity of the cells to ATO as well as the potential mechanisms responsible. shRNA-mediated interference prevented the induction of HO-1, increased cell death, and increased intracellular ROS levels in MG63 cells upon treatment with ATO. Silencing HO-1 increased the susceptibility of MG63 cells to the chemotherapeutic drug ATO by enhancing intracellular accumulation of ROS. Our results suggest that the inhibition of HO-1 could improve the outcome of osteosarcoma treated with ATO.     

Transarterial chemoembolization combined with sorafenib for unresectable hepatocellular carcinoma: a systematic review and meta-analysis

Sorafenib in combination with Transarterial chemoembolization (TACE) is increasingly used in patients with unresectable hepatocellular carcinoma (HCC), but the current evidence is still controversial. The aim of this systematic review was to evaluate the effectiveness and safety of TACE plus sorafenib versus TACE alone for unresectable HCC. We searched PubMed, EMBASE and the Cochrane Library for clinical trials comparing TACE plus sorafenib with TACE alone for unresectable HCC. The study outcomes included overall survival (OS), time to progression (TTP), objective response and adverse events (AEs). Six studies including 1,181 patients were included. Meta-analysis of all studies suggested that the combination therapy group had significant longer OS than TACE group [hazard ratio (HR) = 0.64, 95 % confidence interval (CI) = 0.43–0.97], but the pooled HR of randomized controlled trials (RCTs) failed to achieve statistical significance. For TTP, meta-analysis in both RCTs subgroup and retrospective studies subgroup suggested that combination therapy was superior to TACE group. The combination therapy was also associated with better response to treatment (risk ratio = 1.45, 95 % CI = 1.04–2.02) when both RCTs and retrospective studies were pooled. However, the sorafenib associated AEs were more frequent in the combination therapy group. In conclusion, the combination of TACE and sorafenib is likely to improve OS, TTP and response to treatment when compared with TACE monotherapy. The combination group is also associated with more sorafenib-related AEs.     

Programmed cell death of secretory cavity cells of citrus fruits is associated with Ca2+ accumulation in the nucleus

Key message

An increase in Ca ²⁺ concentration in the nucleus may activate the PCD of secretory cavity cells, and further Ca ²⁺ accumulation contributes to the regulation of nuclear DNA degradation.

Abstract

Calcium plays an important role in plant programmed cell death (PCD). Previously, we confirmed that PCD was involved in the degradation of secretory cavity cells in Citrus sinensis (L.) Osbeck fruits. To further explore the function of calcium in the PCD of secretory cavity cells, we used potassium pyroantimonate precipitation to detect and locate calcium dynamics. At the precursor cell stage of the secretory cavity, Ca²⁺ was only distributed in the cell walls. At the early stage of secretory cavity initial cells, Ca²⁺ in the cell walls was gradually transported into the cytoplasm via pinocytotic vesicles. Although a small amount of Ca²⁺ was present in the nucleus, the TUNEL signal was scarcely observed. At the middle stage of initial cells, a large number of pinocytotic vesicles were transferred to the nucleus, where the vesicle membrane fused with the nuclear membrane to release calcium into the nucleoplasm. In addition, abundant Ca²⁺ aggregated in the condensed chromatin and nucleolus, where the TUNEL signal appeared the strongest. At the late stage of initial cells, the chromatin and nucleolus gradually degraded and disappeared, and the nucleus appeared broken-like, as Ca²⁺ in the cell wall had nearly completely disappeared, and Ca²⁺ in the nucleus was also rapidly reduced. Furthermore, the TUNEL signal also disappeared. These phenomena indicated that an increase in Ca²⁺ concentration in the nucleus might activate the PCD of secretory cavity cells, and further Ca²⁺ accumulation contributed to the regulation of nuclear DNA degradation.     

Assembly and stoichiometry of FliF and FlhA in Salmonella flagellar basal body

The bacterial flagellar export apparatus is required for the construction of the bacterial flagella beyond the cytoplasmic membrane. The membrane‐embedded part of the export apparatus, which consists of FlhA, FlhB, FliO, FliP, FliQ and FliR, is located in the central pore of the MS ring formed by 26 copies of FliF. The C‐terminal cytoplasmic domain of FlhA is located in the centre of the cavity within the C ring made of FliG, FliM and FliN. FlhA interacts with FliF, but its assembly mechanism remains unclear. Here, we fused yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP) to the C‐termini of FliF and FlhA and investigated their subcellular localization by fluorescence microscopy. The punctate pattern of FliF–YFP localization required FliG but neither FliM, FliN, FlhA, FlhB, FliO, FliP, FliQ nor FliR. In contrast, FlhA–CFP localization required FliF, FliG, FliO, FliP, FliQ and FliR. The number of FlhA–YFP molecules associated with the MS ring was estimated to be about nine. We suggest that FlhA assembles into the export gate along with other membrane components during the MS ring complex formation in a co‐ordinated manner.     

Enhancement of riboflavin production by deregulating gluconeogenesis in Bacillus subtilis

The regulation of metabolic flux through glycolytic versus the gluconeogenic pathway plays an important role in central carbon metabolism. In this study, we made an attempt to enhance riboflavin production by deregulating gluconeogenesis in Bacillus subtilis. To this end, gapB (code for NADPH-dependent glyceraldehyde-3-phosphate dehydrogenase), fbp (code for fructose-1,6-bisphosphatase) and pckA (code for phosphoenolpyruvate carboxykinase) were overexpressed in parental strain B. subtilis RH33. Compared with RH33, overexpression of fbp and gapB resulted in approximately 18.0 and 14.2 % increased riboflavin production, respectively, while overexpression of pckA obtained the opposite result. Significant enhancement of riboflavin titers up to 4.89 g/l was obtained in shake flask cultures when gapB and fbp were co-overexpressed, nevertheless the specific growth rate decreased slightly and the specific glucose uptake rate remained almost unchanged. An improvement by 21.9 and 27.8 % of the riboflavin production was achieved by co-overexpression of gapB and fbp in shake flask and fed-batch fermentation, respectively. These results imply that deregulation of gluconeogenesis is an effective strategy for production of metabolites directly stemming from the pentose phosphate pathway as well as other NADPH-demanding compounds with glucose as carbon source in B. subtilis.