Research on the Protective Effect of Twin-groyne Arrangement on Riverbank

A curved channel with intersecting streams can be easily scoured by incoming flow, and the concave bank is badly damaged. This research showed that the twin-groyne could effectively adjust and optimize the flow velocity distribution, change the shape of the free water surface of the bend, prevent erosion, and promote silting on the concave bank, and it could provide a scouring and silting effect on the convex bank. When the spacing of twin-groyne was increased to more than four times the body length of the single-groyne (spur dike), the protective effect on the concave bank was weakened, and the scouring and silting effect of the convex bank was reduced. Excessive spacing of the twin-groyne could cause local erosion damage to the concave bank. When the distance exceeded the theoretical optimum, it was equivalent to the effect of single-groyne. With the increase in the submergence degree, the velocity of the concave bank decreased first and then increased, while the velocity of convex bank decreased continuously. The protective effect of a non-submerged twin-groyne with a dam spacing of four times the body length of the single-groyne was better than that of other conditions, and it is recommended to be used in practice

Efficient open fermentative production of polymer-grade L-lactate from sugarcane bagasse hydrolysate by thermotolerant Bacillus sp. strain P38.

Lactic acid is one of the top 30 potential building-block chemicals from biomass, of which the most extensive use is in the polymerization of lactic acid to poly-lactic-acid (PLA). To reduce the cost of PLA, the search for cheap raw materials and low-cost process for lactic acid production is highly desired. In this study, the final titer of produced L-lactic acid reached a concentration of 185 g·L(-1) with a volumetric productivity of 1.93 g·L(-1)·h(-1) by using sugarcane bagasse hydrolysate as the sole carbon source simultaneously with cottonseed meal as cheap nitrogen sources under the open fed-batch fermentation process. Furthermore, a lactic acid yield of 0.99 g per g of total reducing sugars was obtained, which is very close to the theoretical value (1.0 g g(-1)). No D-isomer of lactic acid was detected in the broth, and thereafter resulted in an optical purity of 100%, which exceeds the requirement of lactate polymerization process. To our knowledge, this is the best performance of fermentation on polymer-grade L-lactic acid production totally using lignocellulosic sources. The high levels of optically pure L-lactic acid produced, combined with the ease of handling and low costs associated with the open fermentation strategy, indicated the thermotolerant Bacillus sp. P38 could be an excellent candidate strain with great industrial potential for polymer-grade L-lactic acid production from various cellulosic biomasses

Metabolic Engineering of <i>Escherichia coli</i> for High-Level Production of (<i>R</i>)-Acetoin from Low-Cost Raw Materials

Acetoin is an important four-carbon platform chemical with versatile applications. Optically pure (R)-acetoin is more valuable than the racemate as it can be applied in the asymmetric synthesis of optically active α-hydroxy ketone derivatives, pharmaceuticals, and liquid crystal composites. As a cytotoxic solvent, acetoin at high concentrations severely limits culture performance and impedes the acetoin yield of cell factories. In this study, putative genes that may improve the resistance to acetoin for Escherichia coli were screened. To obtain a high-producing strain, the identified acetoin-resistance gene was overexpressed, and the synthetic pathway of (R)-acetoin was strengthened by optimizing the copy number of the key genes. The engineered E. coli strain GXASR-49RSF produced 81.62 g/L (R)-acetoin with an enantiomeric purity of 96.5% in the fed-batch fermentation using non-food raw materials in a 3-L fermenter. Combining the systematic approach developed in this study with the use of low-cost feedstock showed great potential for (R)-acetoin production via this cost-effective biotechnological process

Promoter Screening from Bacillus subtilis in Various Conditions Hunting for Synthetic Biology and Industrial Applications.

The use of Bacillus subtilis in synthetic biology and metabolic engineering is highly desirable to take advantage of the unique metabolic pathways present in this organism. To do this, an evaluation of B. subtilis' intrinsic biological parts is required to determine the best strategies to accurately regulate metabolic circuits and expression of target proteins. The strengths of promoter candidates were evaluated by measuring relative fluorescence units of a green fluorescent protein reporter, integrated into B. subtilis' chromosome. A total of 84 predicted promoter sequences located upstream of different classes of proteins including heat shock proteins, cell-envelope proteins, and proteins resistant against toxic metals (based on similarity) and other kinds of genes were tested. The expression levels measured ranged from 0.0023 to 4.53-fold of the activity of the well-characterized strong promoter P43. No significant shifts were observed when strains, carrying different promoter candidates, were cultured at high temperature or in media with ethanol, but some strains showed increased activity when cultured under high osmotic pressure. Randomly selected promoter candidates were tested and found to activate transcription of thermostable β-galactosidase (bgaB) at a similar level, implying the ability of these sequences to function as promoter elements in multiple genetic contexts. In addition, selected promoters elevated the final production of both cytoplasmic bgaB and secreted protein α-amylase to about fourfold and twofold, respectively. The generated data allows a deeper understanding of B. subtilis' metabolism and will facilitate future work to develop this organism for synthetic biology

The effects of neutral protease and cottonseed concentrations for L-lactic acid production.

<p>(a) The effect of the various neutral protease concentrations. (b) The effect of cottonseed concentrations. The error bars in the figure indicate the standard deviations of three parallel replicates.</p

Open fed-batch fermentation from bagasse hydrolysate in fermentor.

<p>Symbols represent carbohydrates consumption and L-lactic acid production in the fermentation medium (g L⁻¹): Total reducing sugars (▪), Glucose (•), and L-lactic acid (▴). The error bars in the figure indicate the standard deviations of three parallel replicates.</p

Additional file 1 of High-yield production of protopanaxadiol from sugarcane molasses by metabolically engineered Saccharomyces cerevisiae

Additional file 1: Table S1. PPD production of engineering Saccharomyces cerevisiae. Table S2. Plasmids used in this study. Table S3. Primers used in this study. Table S4. Primers used for RT-PCR in this study. Table S5. gRNA target sequences used in this study. Figure S1. High-throughput screening of PPD-producing strains. Figure S2. RT-qPCR of PPD-producing strains. Figure S3. PPD production of strain BY-V with glucose/molasses feeding. Figure S4. Construction of Cas9 expression plasmid. Figure S5. PPD production in a 5-L bioreactor. Supplementary Sequences

Scheme of the constructed promoter-probe vector pDL-GFP showing multiple cloning sites (MCS) and restriction enzyme recognition sites.

<p>The boxes show the 5’ and 3’-end enzymes used for ligation of promoter candidates (PC). The left side shows the backbone of the integrated plasmid pDL-GFP and the main genes. On the right side at the bottom the sequences and enzyme sites within it are shown.</p

Strains and plasmids used in this study.

<p>Strains and plasmids used in this study.</p

Comparison of P43 and P<i>trnQ</i> driving α-amylase in pMA5.

<p>A: Enzyme activity of α-amylase that secreted into the medium during fermentation in flasks for 72 h. Error bars represent standard deviations of biological triplicates. B: SDS-PAGE analysis of α-amylase in the supernatant secreted by <i>B</i>. <i>subtilis</i> 1A751. 10 μL of each supernatant sample was loaded on the gel. Lane M: molecular weight marker; Lane 1: pMA5 without α-amylase; Lane 2, 4, 6 represented pMA5 containing P43 after incubation for 36 h, 48 h, and 60 h, respectively. Lane 3, 5, 7 represent pMA5 containing P<i>trnQ</i> after incubation for 36 h, 48 h, and 60 h, respectively.</p