Effect of Overexpression of γ-Tocopherol Methyltransferase on α-Tocopherol and Fatty Acid Accumulation and Tolerance to Salt Stress during Seed Germination in Brassica napus L.

Rapeseed (Brassica napus L.) is an important oil crop and a major source of tocopherols, also known as vitamin E, in human nutrition. Enhancing the quality and composition of fatty acids (FAs) and tocopherols in seeds has long been a target for rapeseed breeding. The gene γ-Tocopherol methyltransferase (γ-TMT) encodes an enzyme catalysing the conversion of γ-tocopherol to α-tocopherol, which has the highest biological activity. However, the genetic basis of γ-TMT in B. napus seeds remains unclear. In the present study, BnaC02.TMT.a, one paralogue of Brassica napus γ-TMT, was isolated from the B. napus cultivar "Zhongshuang11" by nested PCR, and two homozygous transgenic overexpression lines were further characterised. Our results demonstrated that the overexpression of BnaC02.TMT.a mediated an increase in the α- and total tocopherol content in transgenic B. napus seeds. Interestingly, the FA composition was also altered in the transgenic plants; a reduction in the levels of oleic acid and an increase in the levels of linoleic acid and linolenic acid were observed. Consistently, BnaC02.TMT.a promoted the expression of BnFAD2 and BnFAD3, which are involved in the biosynthesis of polyunsaturated fatty acids during seed development. In addition, BnaC02.TMT.a enhanced the tolerance to salt stress by scavenging reactive oxygen species (ROS) during seed germination in B. napus. Our results suggest that BnaC02.TMT.a could affect the tocopherol content and FA composition and play a positive role in regulating the rapeseed response to salt stress by modulating the ROS scavenging system. This study broadens our understanding of the function of the Bnγ-TMT gene and provides a novel strategy for genetic engineering in rapeseed breeding.

[Simultaneous Nitrification and Denitrifying Phosphorus Removal in Continuous Flow Reactor with Intermittent Aeration].

A continuous flow reactor (TCFR) with 10 compartments was used to treat domestic sewage. The anaerobic compartments of TCFR were kept at 3. The anoxic compartments of TCFR were reduced from 2 to 0. Therefore, the aerobic compartments of TCFR were increased gradually from 5 to 7. The aerobic compartments were set to continual aeration in Run1 and intermittent aeration from Run2 to Run4. The aeration/non-aeration ratios were 40 min/20 min,40 min/30 min, and 40 min/40 min, respectively. The nitrification liquid reflux ratios were reduced gradually from 150% to 0%. When the average influent concentrations of COD, NH4+-N, TN, and PO43--P were 259.34, 60.26, 64.42, and 6.10 mg·L-1, respectively, the corresponding effluent concentrations were 26.40, 1.03, 5.84, and 0.3 mg·L-1, respectively in Run4. The nitrogen removal amounts increased gradually from 192.30 mg·h-1 in Run1 to 244.00 mg·h-1 in Run4, and the corresponding removal rates increased from 65.40% to 95.30%. The activity of denitrifying phosphorus accumulating organisms (DPAOs) and phosphorus accumulating organisms (PAOs) increased from 36.05% and 38.20% in Run1 to 140.50% and 133.40% in Run4, respectively. Simultaneous nitrification and denitrifying phosphorus removal was achieved in TCFR by adopting intermittent aeration, which provided a reference for the reformation of sewage treatment plants.

Nitrogen removal from medium-age landfill leachate via post-denitrification driven by PHAs and glycogen in a single sequencing batch reactor.

An anaerobic/aerobic/anoxic (AOA) process in a sequencing batch reactor (SBR) was proposed to treat typical medium-age landfill leachate without extra carbon addition. In a steady-state, the average removal efficiencies of NH4(+)-N, total nitrogen (TN) and COD were 99.7 ± 0.1%, 98.3 ± 0.3% and 89.8 ± 1.4%, when influent NH4(+)-N, TN and COD were 1025-1327 mg/L, 1346-1854 mg/L and 6430-9372 mg/L, respectively. In the anaerobic stage, dissolved organic matter was taken up partially and stored as polyhydroxyalkanoates (PHAs) with concomitant consumption of glycogen. In the aerobic stage, PHAs was oxidized and glycogen was replenished in the bacterial cells, when TN of 75.4 mg/L was removed via simultaneous nitrification and denitrification (SND). The residual nitrate and nitrite were denitrified completely by utilizing residual PHAs and glycogen as electron donors in the anoxic phase. Denitrifying glycogen accumulating organisms (GAOs) were considered to be playing the major role in the process.

Improvement of nutrient removal by optimizing the volume ratio of anoxic to aerobic zone in AAO-BAF system.

A two-sludge system, combining anaerobic/anoxic/aerobic process with biological aerated filter (AAO-BAF), is used to treat domestic wastewater with low COD/N ratio (around 3.6). The volume ratio of anoxic to aerobic zone (Vano/Vaer) of the AAO reactor gradually increased from 2:5 to 6:1, during which the nutrient removal was improved. However, phosphorous removal began to deteriorate noticeably while Vano/Vaer increased to 7:0. The favorable Vano/Vaer was between 2.5:1 and 6:1. When Vano/Vaer was 6:1, the average removal efficiencies of COD, TN and PO4(3-) were 89±4%, 83±3% and 99±1%, respectively. This study suggested the AAO-BAF system could achieve efficient nitrogen and phosphorous removal with limited carbon source.