Transcriptome analysis of Rhizopus oryzae seed pellet formation using triethanolamine

Abstract

Rhizopus oryzae (R. oryzae) can effectively produce organic acids, and its pellet formation in seed cultures has been shown to significantly enhance subsequent fermentation processes. Despite advances in strain development, simple and effective methods for inducing pellet morphology and a basic understanding of the mechanisms controlling this process could facilitate substantial increases in efficiency and product output. Here, we report that 1.5% triethanolamine (TEOA) in seed culture medium can activate the growth of R. oryzae spores in compact and uniform pellets which is optimal for fermentation conditions. Analysis of fermentation kinetics showed that the production of fumaric and L-malic acid increases 293% and 177%, respectively. Transcriptomic analysis revealed that exposure of R. oryzae to 1.5% TEOA during the seed culture activated the phosphatidylinositol and mitogen-activated protein kinase signaling pathways. Theses pathways subsequently stimulated the downstream carbohydrate-active synthases and hydrolases that required for cell wall component synthesis and reconstruction. Our results thus provide insight into the regulatory pathways controlling pellet morphology germane to the viability of seed cultures, and provide valuable reference data for subsequent optimization of organic acid fermentation by R. oryzae.

Dynamic Optimization of Lactic Acid Production from Grape Stalk Solid-State Fermentation with Rhizopus oryzae Applying a Variable Temperature Profile

“…This field of study is called morphological engineering. For example, in [43], the authors were able to form compact and uniform granules of R. oryzae by adding triethanolamine to the culture medium, which resulted in a 293% increase in malic acid production and a 177% increase in fumaric acid production. In our work, when mycelial growth occurred (22 and 35 • C), no t d was observed, and pellet growth occurred at 40 • C, t d = 0.7 h. It is plausible that R. oryzae requires additional time to adapt to pellet growth conditions before initiating LA production.…”

Improving the productivity of malic acid by alleviating oxidative stress during Aspergillus niger fermentation

“…Excessive CO 2 emissions along with depletion of fossil fuel resources have led to the problems of global warming and energy crisis. Microorganisms were utilized to transform renewing biomass into fuels and chemicals in the field of biorefinery, which provides a perspective orientation to address those concerns [27,37,38]. Numerous of microbes have been utilized to produce malic acid by metabolic engineering and fermentation optimization [39][40][41].…”

“…As in previous studies [27], in brief, 15 parallel shake flasks were set for each group during the fermentation process. We take 3 shake flasks from the shaker when taking samples every day.…”

Improving the productivity of malic acid by alleviating oxidative stress during Aspergillus niger fermentation

“…Excessive CO 2 emissions along with depletion of fossil fuel resources have led to the problems of global warming and energy crisis. Microorganisms were utilized to transform renewing biomass into fuels and chemicals in the eld of biore nery, which provides a perspective orientation to address those concerns [27,51,52]. Numerous of microorganisms were utilized to produce malic acid, including metabolic engineering and fermentation optimization [53][54][55].…”

“…As in previous studies [27], in brief, 2 mL of the fermentation samples were transferred into a 10-mL tube, and the same volume of 2 M hydrochloric acid (HCl) was used to dissolve excess CaCO 3 . Then, the mixture was added to 2-mL tubes and centrifuged at 11000 rcf for 10 min.…”