Thermal-tolerant potential of ordinary Chlorella pyrenoidosa and the promotion of cell harvesting by heterotrophic cultivation at high temperature.

During the heterotrophic cultivation of microalgae, a cooled process against temperature rise caused by the metabolism of exogenous organic carbon sources greatly increases cultivation cost. Furthermore, microalgae harvesting is also a cost-consuming process. Cell harvesting efficiency is closely related to the characteristics of the algal cells. It may be possible to change cell characteristics through controlling culture conditions to make harvesting easier. In this study, the mesophilic Chlorella pyrenoidosa was found to be a thermal-tolerant species in the heterotrophic mode. The cells could maintain their maximal specific growth rate at 40°C and reached 1.45 day-1, which is equivalent to that of cultures at 35°C but significantly higher than those cultured at lower temperatures. Interestingly, the cells cultured at 40°C were much easier to be harvested than those at lower temperatures. The harvesting efficiency of the cells cultured at 40°C reached 96.83% after sedimentation for 240 min, while the cells cultured at lower temperatures were reluctant to settle. Likely, the same circumstance occurred when cells were harvested by centrifugation or flocculation. The promotion of cell harvesting for cells cultured at high temperatures was mainly attributed to increased cell size and decreased cell surface charge. To the best of our knowledge, this is the first report that cells cultured at high temperatures can promote microalgae harvesting. This study explores a new approach to simplify the cultivation and harvesting of microalgae, which effectively reduces the microalgae production cost.

One-step co-cultivation and flocculation of microalgae with filamentous fungi to valorize starch wastewater into high-value biomass.

A novel method of one-step co-cultivation and harvesting of microalgae and fungi, for efficient starch wastewater treatment and high-value biomass production was developed. By combination of Aspergillus oryzae and Chlorella pyrenoidosa, nutrients in wastewater could be converted to useful microbial biomass, while the wastewater was purified. Moreover, the microalgae C. pyrenoidosa could gradually be encapsulated in fungal pellets which promoted the biomass harvesting. The free algal cells could be completely harvested by fungal pellets within 72 h. The synergistic effects between them greatly improved the removal efficiencies of main pollutants as the removal efficiency of COD, TN, and TP reached 92.08, 83.56, and 96.58 %, respectively. In addition, the final biomass concentration was higher than that of individual cultures. The protein and lipid concentration was also significantly improved and reached 1.92 and 0.99 g/L, respectively. This study provides a simple and efficient strategy for simultaneous wastewater treatment and high-value biomass production.

[Y chromosome microdeletions, chromosome karyotypes and reproductive hormones in patients with azoospermia and severe oligozoospermia].

OBJECTIVE: To study the correlation of azoospermia and severe oligozoospermia with Y chromosome microdeletions, chromosome karyotype and reproductive hormones in male infertility patients. METHODS: We collected semen samples from 63 patients with azoospermia, 49 with severe oligozoospermia and 60 men with normal semen parameters, and determined the incidence of Y chromosome microdeletions, chromosome karyotypes and the levels of reproductive hormones. RESULTS: The incidence rate of Y chromosome microdeletions was 11.11% in the azoospermia and 8.16% in the severe oligozoospermia patients, as compared with 0 in the normal controls (P<0.05). The rate of chromosome abnormalities was 9.52% in the azoospermia group, with statistically significant differences from the severe oligozoospermia and normal control men (both 0) (P<0.05). The levels of FSH and LH were significantly higher in the azoospermia ([20.41 +/- 19.34] IU/L and [11.44 +/- 9.48] IU/L) and the severe oligozoospermia patients ([8.88 +/- 7.04] IU/L and [6.78 +/- 3.85] IU/L) than in the normal males ([3.88 +/- 2.21] IU/L and [4.63 +/- 1.51] IU/L) (P<0.05). CONCLUSION: Examinations of genetics and reproductive hormones are necessary for infertile males with azoospermia and severe oligozoospermia, which may contribute to early diagnosis and treatment.

Alterations in the frequency of trinucleotide repeat dynamic mutations in offspring conceived through assisted reproductive technology.

STUDY QUESTION: How does the frequency of trinucleotide repeat dynamic mutations in offspring conceived through assisted reproductive technology (ART) compare with the frequency of these mutations in control offspring conceived from spontaneous pregnancies? SUMMARY ANSWER: There is a slight increase in dynamic mutation instability in offspring conceived through ART compared with the naturally conceived offspring. WHAT IS KNOWN ALREADY: There is evidence to suggest that ART can increase the risk of birth defects and karyotypic abnormalities. However, the accumulating evidence of an association between ART and de novo genetic aberrations is controversial. STUDY DESIGN, SIZE, DURATION: A prospective clinical observational study was performed on 246 families recruited from an in vitro fertilisation (IVF) centre at a tertiary-care, university-affiliated teaching hospital from 2008 to 2012. The study included 147 ART families [75 IVF and 72 intracytoplasmic sperm injection (ICSI)] in the study group and 99 natural-conception families in the control group. PARTICIPANTS, SETTING, METHODS: Parental, umbilical cord and infant peripheral blood samples were collected, and the trinucleotide repeats of the ATN1, AR, ATXN1, ATXN3, Huntington, DMPK and FMR-1 genes were investigated between the generations; these genes were chosen due to their ability to undergo dynamic mutation. The frequencies and sizes of the mutational repeats, as well as the intergenerational instability, were measured. MAIN RESULTS AND THE ROLE OF CHANCE: In 2466 transmissions identified in the ART offspring, 2.11% (n = 52/2466) of the alleles were unstable upon transmission, while in the control group offspring, the frequency of dynamic mutation was 0.77% (n = 10/1300); this difference was statistically significant (P < 0.01). The unstable transmission alleles were detected in 32 (2.48%) of the 1288 alleles from the IVF offspring and in 20 (1.70%) of the 1178 alleles from the ICSI offspring; both of these frequencies were significantly different from that of naturally conceived offspring (0.77%) (P < 0.01 and P < 0.05, respectively). However, there were no significant differences in the sizes of the mutational repeats or in the rates of expansion or contraction among the three groups (P > 0.05). The repeat copy numbers of the examined genes were found to be within the normal ranges in all parents and infants. LIMITATIONS, REASONS FOR CAUTION: One strength of our study is the relatively large sample size; we were able to detect mutations in seven common dynamic genes, and this large sample size allowed us to detect unstable alleles. Although we observed a clear alteration in the frequency of dynamic mutation in the ART offspring compared with controls, further studies are urgently needed to confirm this observation and determine the cause of this phenomenon. WIDER IMPLICATIONS OF THE FINDINGS: DNA microsatellite analysis provides an important tool to assess genomic instability. In this study, we report an association between ART and the frequency of dynamic mutation. The instability could be a reflection of the core infertility problem, the controlled ovarian hyperstimulation and/or the in vitro culture conditions.