Alkaliphilic and Alkali-Tolerant Algae

Gimmler, H.; Degenhard, B.

doi:10.1007/978-3-642-59491-5_10

Cited by 37 publications

(6 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One possible explanation for the negative effect of high pH on growth and photosynthesis might be the inability of a species to generate its membrane potential when ∆pH over the plasma membrane changes and the external pH becomes higher than the internal one. The H + -ATPases are among the first to be inhibited (Gimmler and Degenhardt 2001) and many nutrient uptake processes are hampered.…”

Section: Discussionmentioning

confidence: 99%

Negative Effects of P-Buffering and pH on Photosynthetic Activity of Planktonic Desmid Species

Spijkerman¹,

García‐Mendoza²,

Matthijs³

et al. 2004

Photosynt.

View full text Add to dashboard Cite

The photosynthetic activities of three planktonic desmid species (Staurastrum brachiatum, Staurodesmus cuspidatus var. curvatus, and Staurastrum chaetoceras) were compared after adaptation to medium enriched with either a 20 mM Na +phosphate (P) or HEPES buffer. Incubations up to 2 d were carried out at pH 6 or 8 under normal air or air enriched with 5 % CO 2 . Gross maximum photosynthetic rate (P max ) and growth rate were decreased in both S. brachiatum and Std. cuspidatus at higher pH when using the HEPES buffer and this effect was independent of CO 2 concentration, indicating that pH had an inhibitory effect on photosynthesis and growth in these species. The P-buffer at pH 8 caused a large decrease in P max and quantum yield for charge separation in photosystem 2 (PS2), compared to HEPES-buffered algae. This effect was very large in both S. brachiatum and Std. cuspidatus, two species characteristic of soft water lakes, but also significant in S. chaetoceras, a species dominant in eutrophic, hard water lakes. The decreased P max in P-buffer could not be related to a significant increase in cellular P content known to be responsible for inhibition in isolated chloroplasts. Experiments at pH 6 and 8 showed that two conditions, high pH and high Na + concentration, both contributed to the decreased P max and quantum yield in the desmids. Effects of a P-buffer were less pronounced by using K + -P buffer. The use of P-buffer at pH 8 possibly resulted in high irradiance stress in all species, indicated by damage in the PS2 core complex. In the soft water species pH 8 resulted in increased non-photochemical quenching together with a high de-epoxidation state of the xanthophyll cycle pigments.

show abstract

Section: Discussionmentioning

confidence: 99%

Negative Effects of P-Buffering and pH on Photosynthetic Activity of Planktonic Desmid Species

Spijkerman¹,

García‐Mendoza²,

Matthijs³

et al. 2004

Photosynt.

View full text Add to dashboard Cite

show abstract

“…Under these extreme conditions, cells require additional energy to regulate intracellular pH. It has been previously suggested that alkali-tolerant or alkaliphilic microalgae regulate the cytosolic pH to (∼8.0) against the natural H + gradient (low outside and high inside) by maintenance of an oppositely directed Na + gradient (high outside and low inside) across the cell membrane 26 by continuous influx and efflux of Na + (Na + -dependent cycle). Since the internal Na + level of alkali-tolerant microalgae is likely far lower than the external concentration and the membrane potential is negative, the uptake of Na + is downhill and does not require energy.…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, Na + export out of the cell is uphill, requiring energy which is derived from ATP hydrolysis through a primary sodium pump (Na + −ATPase). 26 When challenged with a requirement of a nearly 100-fold higher H + gradient at pH > 10 than at pH 8.4, it likely that the higher energy demand to maintain cellular pH led to an increase in fermentative cell metabolism and higher organic acid production rate. In addition to more rapid cellular organic acid production (to meet energy requirements of the cell in high pH environments), favorable conditions for neutralization of the produced organic acids in the high pH extracellular medium could also increase secretion rates.…”

Section: Resultsmentioning

confidence: 99%

“…Since the internal Na + level of alkali-tolerant microalgae is likely far lower than the external concentration and the membrane potential is negative, the uptake of Na + is downhill and does not require energy. In contrast, Na + export out of the cell is uphill, requiring energy which is derived from ATP hydrolysis through a primary sodium pump (Na + –ATPase) . When challenged with a requirement of a nearly 100-fold higher H + gradient at pH > 10 than at pH 8.4, it likely that the higher energy demand to maintain cellular pH led to an increase in fermentative cell metabolism and higher organic acid production rate.…”

Section: Resultsmentioning

confidence: 99%

“…In this study, we tested the hypothesis that autofermentation at extreme alkaline pH (>10) would increase autofermentation rates since the energy cost to maintain pH homeostatis would be higher and would result in greater cellular catabolism rates. 26 To assess the broad applicability of our results, we investigated strains from two microalgal genera and one cyanobacterial genus, that are frequently considered for commercial cultivationChlorella sp., Scenedesmus sp., and Synecococcus sp. We assessed fermentation kinetics as well as yield and distribution of the fermentation end products.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Production of Organic Acids via Autofermentation of Microalgae: A Promising Approach for Sustainable Algal Biorefineries

Pendyala

Hanifzadeh

Abel

et al. 2020

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

We demonstrate a facile and simple method for the direct conversion of microalgae biomass into organic acids via self-anaerobic metabolism in the dark (autofermentation). This one-step method does not require the use of additional catalysts (chemicals or enzymes), occurs at ambient temperature, and uses wet microalgae biomass as feed. We studied the effect of pH, salinity, and biomass concentration on the organic acid yield, rate of fermentation, and the ability of microalgae to ferment free sugars amended to the microalgae feedstocks. Our results show that when autofermentation of microalgae biomass was performed at extreme alkaline pH (>10), ∼90% of the degraded organic carbon was recovered as organic acids. Also, relative to mildly alkaline pH (8.4), a 4- to 6.5-fold enhancement in fermentation rates was observed at extreme alkaline pH (10.4) for the microalgae Chlorella sorokiniana SLA-04 and Scenedesmus obliquus UTEX 393 as well as the cyanobacterium Synechococcus elongatus UTEX 2973. The results also showed that both cellular carbohydrates and proteins were degraded during autofermentation, although the yields of organic acids from carbohydrates were higher. The lipids appear to be conserved in the residues and could potentially be extracted after autofermentation for further conversion. Externally added sugars could also be fermented in addition to cellular organic carbon. Overall, the autofermentation approach is suitable for conversion of lipid-lean, but carbohydrate- and protein-rich microalgae biomass that is typically produced in mass cultivations that target high biomass productivity.

show abstract