Dataset Information

Sequential phototrophic-mixotrophic cultivation of oleaginous microalga Graesiella sp. WBG-1 in a 1000 m² open raceway pond.

ABSTRACT:

Background

Microalgae are an important feedstock in industries. Currently, efforts are being made in the non-phototrophic cultivation of microalgae for biomass production. Studies have shown that mixotrophy is a more efficient process for producing algal biomass in comparison to phototrophic and heterotrophic cultures. However, cultivation of microalgae in pilot-scale open ponds in the presence of organic carbon substrates has not yet been developed. The problems are heterotrophic bacterial contamination and inefficient conversion of organic carbon.

Results

Laboratory investigation was combined with outdoor cultivation to find a culture condition that favors the growth of alga, but inhibits bacteria. A window period for mixotrophic cultivation of the alga Graesiella sp. WBG-1 was identified. Using this period, a new sequential phototrophic-mixotrophic cultivation (SPMC) method that enhances algal biomass productivity and limits bacteria contamination at the same time was established for microalgae cultivation in open raceway ponds. Graesiella sp. WBG-1 maximally produced 12.5 g biomass and 4.1 g lipids m^-2 day^-1 in SPMC in a 1000 m² raceway pond, which was an over 50% increase compared to phototrophic cultivation. The bacterial number in SPMC (2.97?×?10⁵ CFU ml^-1) is comparable to that of the phototrophic cultivations.

Conclusions

SPMC is an effective and feasible method to cultivate lipid-rich microalgae in open raceway ponds. Successful scale-up of SPMC in a commercial raceway pond (1000 m² culture area) was demonstrated for the first time. This method is attractive for global producers of not only lipid-rich microalgae biomass, but also astaxanthin and ?-carotene.

SUBMITTER: Wen X

PROVIDER: S-EPMC6371596 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Sequential phototrophic-mixotrophic cultivation of oleaginous microalga <i>Graesiella</i> sp. WBG-1 in a 1000 m<sup>2</sup> open raceway pond.

Wen Xiaobin X Tao Huanping H Peng Xinan X Wang Zhongjie Z Ding Yi Y Xu Yan Y Liang Lin L Du Kui K Zhang Aoqi A Liu Caixia C Geng Yahong Y Li Yeguang Y

Biotechnology for biofuels 20190211

<h4>Background</h4>Microalgae are an important feedstock in industries. Currently, efforts are being made in the non-phototrophic cultivation of microalgae for biomass production. Studies have shown that mixotrophy is a more efficient process for producing algal biomass in comparison to phototrophic and heterotrophic cultures. However, cultivation of microalgae in pilot-scale open ponds in the presence of organic carbon substrates has not yet been developed. The problems are heterotrophic bacter ...[more]

PMID: 30805027

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Project description:To reduce water utilization, limit environmental pollution, and guarantee aquatic production and quality, the in-pond raceway recirculating culture system (IPRS) has been developed and is widely used. The effectiveness and sustainability of IPRSs rely on a good understanding of the ecological processes related to bacterial communities in the purification area. In this study, we investigated the dynamics and assembly mechanisms of benthic bacterial communities in the purification area of an industrial-scale IRPS. We found significant temporal and spatial variations in the sediment characteristics and benthic bacterial communities of the IPRS, although correlation analyses revealed a very limited relationship between them. Among the different culture stages, we identified numerous benthic bacteria with different abundances. Abundances of the phyla Bacteroidota and Desulfobacterota decreased whereas those of Myxococcota and Gemmatimonadota increased as the culture cycle progressed. Co-occurrence networks revealed that the bacterial community was less complex but more stable in the IPRS at the final stage compared with the initial stage. The neutral community model (NCM) showed that stochastic processes were the dominant ecological processes shaping the assembly of the benthic bacterial community. The null model suggested that homogenizing dispersal was more powerful than dispersal limitation and drift in regulating the assembly of the community. These findings indicate that the benthic microbial communities in purification areas of the IPRS may not be affected by the deposited wastes, and a more stable benthic microbial communities were formed and mainly driven by stochastic processes. However, the benthic microbial communities in the purification area at the end of the culturing stage was characterized by potentially inhibited organic matter degradation and carbon and sulfur cycling abilities, which was not corresponding to the purification area's function. From this point on, the IPRS, especially the purification area was needed to be further optimized and improved.

Project description:UNLABELLED: BACKGROUND:The lack of sequenced genomes for oleaginous microalgae limits our understanding of the mechanisms these organisms utilize to become enriched in triglycerides. Here we report the de novo transcriptome assembly and quantitative gene expression analysis of the oleaginous microalga Neochloris oleoabundans, with a focus on the complex interaction of pathways associated with the production of the triacylglycerol (TAG) biofuel precursor. RESULTS:After growth under nitrogen replete and nitrogen limiting conditions, we quantified the cellular content of major biomolecules including total lipids, triacylglycerides, starch, protein, and chlorophyll. Transcribed genes were sequenced, the transcriptome was assembled de novo, and the expression of major functional categories, relevant pathways, and important genes was quantified through the mapping of reads to the transcriptome. Over 87 million, 77 base pair high quality reads were produced on the Illumina HiSeq sequencing platform. Metabolite measurements supported by genes and pathway expression results indicated that under the nitrogen-limiting condition, carbon is partitioned toward triglyceride production, which increased fivefold over the nitrogen-replete control. In addition to the observed overexpression of the fatty acid synthesis pathway, TAG production during nitrogen limitation was bolstered by repression of the ?-oxidation pathway, up-regulation of genes encoding for the pyruvate dehydrogenase complex which funnels acetyl-CoA to lipid biosynthesis, activation of the pentose phosphate pathway to supply reducing equivalents to inorganic nitrogen assimilation and fatty acid biosynthesis, and the up-regulation of lipases-presumably to reconstruct cell membranes in order to supply additional fatty acids for TAG biosynthesis. CONCLUSIONS:Our quantitative transcriptome study reveals a broad overview of how nitrogen stress results in excess TAG production in N. oleoabundans, and provides a variety of genetic engineering targets and strategies for focused efforts to improve the production rate and cellular content of biofuel precursors in oleaginous microalgae.

Dataset Information

Sequential phototrophic-mixotrophic cultivation of oleaginous microalga Graesiella sp. WBG-1 in a 1000 m² open raceway pond.

Background

Results

Conclusions

Publications

Sequential phototrophic-mixotrophic cultivation of oleaginous microalga <i>Graesiella</i> sp. WBG-1 in a 1000 m<sup>2</sup> open raceway pond.

Similar Datasets

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Dataset Information

Sequential phototrophic-mixotrophic cultivation of oleaginous microalga Graesiella sp. WBG-1 in a 1000 m2 open raceway pond.

Background

Results

Conclusions

Publications

Sequential phototrophic-mixotrophic cultivation of oleaginous microalga <i>Graesiella</i> sp. WBG-1 in a 1000 m<sup>2</sup> open raceway pond.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Sequential phototrophic-mixotrophic cultivation of oleaginous microalga Graesiella sp. WBG-1 in a 1000 m² open raceway pond.