Characteristics of purple nonsulfur bacteria grown under Stevia residue extractions

Abstract

Significance and Impact of the Study: This study first reported that the purple nonsulfur bacteria could grow well and possess high quality using Stevia residue extractions as carbon source. Those results suggest that wastewater of Stevia residue can be a favourable substrate for microbial growth, which can further provide desired bioresources for the application of downstream industry. AbstractAs a consequence of the large-scale cultivation of Stevia plants, releases of plant residues, the byproduct after sweetener extraction, to the environment are inevitable. Stevia residue and its effluent after batching up contain large amounts of organic matters with small molecular weight, which therefore are a potential pollution source. Meanwhile, they are favourite substrates for microorganism growths. This investigation was aimed to utilize the simulated effluent of Stevia residue to enrich the representative purple nonsulfur bacterium (PNSB), Rhodopseudomonas palustris (Rps. palustris), which has important economic values. The growth profile and quality of Rps. palustris were characterized by spectrophotometry, compared to those grown in common PNSB mineral synthetic medium. Our results revealed that the simulated effluent of Stevia residue not only stimulated Rps. palustris growth to a greater extent, but also increased its physiologically active cytochrome concentrations and excreted indole-3-acetic acid (IAA) content. This variation in phenotype of Rps. palustris could result from the shift in its genotype, further revealed by the repetitive sequence-based PCR (rep-PCR) fingerprinting analysis. Our results showed that the effluent of Stevia residue was a promising substrate for microbial growth.

The foliar spray of Rhodopseudomonas palustris grown under Stevia residue extract promotes plant growth via changing soil microbial community

“…Particularly, R. palustris grown under Stevia residue extract showed more remarkable influence, which might be attributed to the individual characteristics of R. palustris. As shown in our preceding report, R. palustris grown under Stevia residue extract has higher cytochrome content in live cells as compared to that grown under the chemical medium (Xu et al 2013a). Besides, our unpublished data showed that the ability of excreting 5-aminolevulinic acid (5-ALA) was also high in the R. palustris grown under Stevia residue extract.…”

“…The NH 4 Cl is a common N source, while L-tryptophan is the precursor of indole-3-acetic acid (IAA), a typical phytohormone regulating various developmental and physiological processes in plants ( Kim et al 2004). Our preceding report has shown that R. palustris exhibits distinct growth pattern and genotypic characteristics under such N sources (Xu et al 2013a). Yet, whether those changes would influence the downstream application of R. palustris is still unknown so far.…”

“…After sweetener extraction, the residue of Stevia produces large amounts of wastewater rich in organic components suitable for the growth of beneficial microbes, such as a representative purple nonsulfur bacterium, Rhodopseudomonas palustris. However, given the high C/N ratio of Stevia residue extract (Xu et al 2013a), it is necessary to supplement nitrogen (N) sources with the aim of satisfying microbial growth, e.g., NH 4 Cl or L-tryptophan. The NH 4 Cl is a common N source, while L-tryptophan is the precursor of indole-3-acetic acid (IAA), a typical phytohormone regulating various developmental and physiological processes in plants ( Kim et al 2004).…”

“…The Stevia residue extract was used as the culture medium for R. palustris. The detailed extracting procedure (at 20-25°C) and the chemical properties of the extract were described in our previous report (Xu et al 2013a). The concentrations of total organic carbon (C) and total N in the Stevia residue extract were 605 and 20.5 mg/L, respectively.…”

Development of a low-cost culture medium for the rapid production of plant growth-promoting Rhodopseudomonas palustris strain PS3

“…The cost is primarily due to expensive nitrogen sources, such as yeast extract and peptone. On the other hand, some media have low-cost sources; for example, Xu et al [31] used Stevia residue extractions supplied with NH 4 Cl as a medium to culture R. palustris, and the highest obtained biomass was 1.5 (OD 660 ) (approximately equivalent to 0.77 g/L) after 96 hours of cultivation. Kornochalert et al [9] obtained the 0.9 g/L R. palustris in latex rubber sheet wastewater supplied with pineapple extract after 96 hours of fermentation.…”