Comparative transcriptomics and transcriptional regulation analysis of enhanced laccase production induced by co-culture of Pleurotus eryngii var. ferulae with Rhodotorula mucilaginosa.
Zhang Qi,Zhao Liting,Li YouRan,Wang Feng,Li Song,Shi Guiyang,Ding Zhongyang
Applied microbiology and biotechnology
The co-culturing of Pleurotus eryngii var. ferulae and Rhodotorula mucilaginosa was confirmed in our previous studies to be an efficient strategy to improve laccase production by submerged fermentation. To determine the possible regulation principles underlying this behaviour, comparative transcriptomic analysis was performed on P. eryngii var. ferulae to investigate the differential expression of genes in co-culture. RNA-seq analysis showed that genes concerning xenobiotic biodegradation and expenditure of energy were upregulated. However, genes related to oxidative stress were downregulated. In addition, the transcription levels of laccase isoenzymes were not consistent in the co-culture system: 3 laccase genes (lacc1, lacc2, lacc12) were upregulated, and 3 laccase genes (lacc4, lacc6, lacc9) were downregulated. The enhancement in laccase activity can be due to upregulation of a laccase heterodimer encoded by the genes lacc2 and ssPOXA3a (or ssPOXA3b), whose expression levels were increased by 459% and 769% (or 585% for ssPOXA3b) compared with those of a control, respectively. β-Carotene produced by R. mucilaginosa upregulated the transcription of lacc2 only. Combining these results with an analysis of cis-acting responsive elements indicated that four transcription factors (TFs) had potential regulatory effects on the transcription of laccase genes. It was supposed that TFa regulated lacc transcription by binding with methyl jasmonate and heat shock response elements. The expression of TFb, TFc, and TFd was regulated by β-carotene. However, β-carotene had no effect on TFa expression. These results provide a possible mechanism for the regulation of laccase gene transcription in the co-culture system and are also beneficial for the future intensification of fungal laccase production.
Algal-fungal symbiosis leads to photosynthetic mycelium.
Du Zhi-Yan,Zienkiewicz Krzysztof,Vande Pol Natalie,Ostrom Nathaniel E,Benning Christoph,Bonito Gregory M
Mutualistic interactions between free-living algae and fungi are widespread in nature and are hypothesized to have facilitated the evolution of land plants and lichens. In all known algal-fungal mutualisms, including lichens, algal cells remain external to fungal cells. Here, we report on an algal-fungal interaction in which algal cells become internalized within the hyphae of the fungus . This apparent symbiosis begins with close physical contact and nutrient exchange, including carbon and nitrogen transfer between fungal and algal cells as demonstrated by isotope tracer experiments. This mutualism appears to be stable, as both partners remain physiologically active over months of co-cultivation, leading to the eventual internalization of photosynthetic algal cells, which persist to function, grow and divide within fungal hyphae. and are biotechnologically important species for lipids and biofuel production, with available genomes and molecular tool kits. Based on the current observations, they provide unique opportunities for studying fungal-algal mutualisms including mechanisms leading to endosymbiosis.
Attachment between heterotrophic bacteria and microalgae influences symbiotic microscale interactions.
Samo Ty J,Kimbrel Jeffrey A,Nilson Daniel J,Pett-Ridge Jennifer,Weber Peter K,Mayali Xavier
The surface and surroundings of microalgal cells (phycosphere) are critical interaction zones but have been difficult to functionally interrogate due to methodological limitations. We examined effects of phycosphere-associated bacteria for two biofuel-relevant microalgal species (Phaeodactylum tricornutum and Nannochloropsis salina) using stable isotope tracing and high spatial resolution mass spectrometry imaging (NanoSIMS) to quantify elemental exchanges at the single-cell level. Each algal species responded differently to bacterial attachment. In P. tricornutum, a high percentage of cells had attached bacteria (92%-98%, up to eight bacteria per alga) and fixed 64% more carbon with attached bacteria compared to axenic cells. In contrast, N. salina cells were less commonly associated with bacteria (42%-63%), harboured fewer bacteria per alga, and fixed 10% more carbon without attached bacteria compared to axenic cells. An uncultivated bacterium related to Haliscomenobacter sp. was identified as an effective mutualist; it increased carbon fixation when attached to P. tricornutum and incorporated 71% more algal-fixed carbon relative to other bacteria. Our results illustrate how phylogenetic identity and physical location of bacteria and algae facilitate diverse metabolic responses. Phycosphere-mediated, mutualistic chemical exchanges between autotrophs and heterotrophs may be a fruitful means to increase microalgal productivity for applied engineering efforts.
Screening of microalgae for integral biogas slurry nutrient removal and biogas upgrading by different microalgae cultivation technology.
Wang Xue,Bao Keting,Cao Weixing,Zhao Yongjun,Hu Chang Wei
The microalgae-based technology has been developed to reduce biogas slurry nutrients and upgrade biogas simultaneously. In this work, five microalgal strains named Chlorella vulgaris, Scenedesmus obliquus, Selenastrum capricornutum, Nitzschia palea, and Anabaena spiroides under mono- and co-cultivation were used for biogas upgrading. Optimum biogas slurry nutrient reduction could be achieved by co-cultivating microalgae (Chlorella vulgaris, Scenedesmus obliquus, and Nitzschia palea) with fungi using the pelletization technology. In addition, the effects of different ratio of mixed LED light wavelengths applying mixed light-emitting diode during algae strains and fungi co-cultivation on CO and biogas slurry nutrient removal efficiency were also investigated. The results showed that the COD (chemical oxygen demand), TN (total nitrogen), and TP (total phosphorus) removal efficiency were 85.82 ± 5.37%, 83.31 ± 4.72%, and 84.26 ± 5.58%, respectively at red: blue = 5:5 under the co-cultivation of S. obliquus and fungi. In terms of biogas upgrading, CH contents were higher than 90% (v/v) for all strains, except the co-cultivation with S. obliquus and fungi at red: blue = 3:7. The results indicated that co-cultivation of microalgae with fungi under mixed light wavelengths treatments was most successful in nutrient removal from wastewater and biogas upgrading.
Simultaneously upgrading biogas and purifying biogas slurry using cocultivation of Chlorella vulgaris and three different fungi under various mixed light wavelength and photoperiods.
Cao Weixing,Wang Xue,Sun Shiqing,Hu Changwei,Zhao Yongjun
In order to purify biogas slurry and biogas simultaneously, three different fungi, Pleurotus geesteranus (P. geesteranus), Ganoderma lucidum (G. lucidum), and Pleurotus ostreatus (P. ostreatus) were pelletized with Chlorella vulgaris (C. vulgaris). The results showed that the optimal light wavelength ratio for red:blue was 5:5 for these three different fungi-assisted C. vulgaris, resulting in higher specific growth rate as well as nutrient and CO removal efficiency compared with other ratios. G. lucidum/C. vulgaris was screened as the best fungi-mialgae for biogas slurry purification and biogas upgrading with light/dark ratio of 14h:10h, which was also confirmed by the economic efficiency analysis of the energy consumptions. These results will provide a theoretical foundation for large-scale biogas slurry purifying and biogas upgrading using microalgae.
Influence of three microalgal-based cultivation technologies on different domestic wastewater and biogas purification in photobioreactor.
Sun Shiqing,Hu Changwei,Gao Shumei,Zhao Yongjun,Xu Jie
Water environment research : a research publication of the Water Environment Federation
To investigate the effects of different microalgae and culture methods on the purification of domestic wastewater and biogas, Chlorella vulgaris and Scenedesmus obliquus were selected. Three different culture methods (monoculture, microalgal-fungi cocultivation, and microalgal-activated sludge cocultivation) were used to remove nutrients from four different domestic wastewaters and remove CO from raw biogas in a photobioreactor. The results show that the effluent from the centrate of pretreated urban wastewater (WW4) achieved the highest nutrient and CO removal efficiency. Cocultivation of C. vulgaris and activated sludge achieved the highest COD, TP, and CO removal efficiencies of 79.27%, 81.25%, and 60.39% with WW4, respectively. Cocultivation of C. vulgaris and fungi achieved the highest TN removal efficiency of 78.46% with WW4. The contents of C, N, and P in the microalgal-activated sludge symbiont after treatment exceeded 50%, 8%, and 0.8%, respectively. Highly economically efficient energy consumption was achieved with WW4 for both C. vulgaris and S. obliquus. Microalgal-activated sludge cocultivation was identified as the optimal option for the simultaneous purification of wastewater and biogas based on its high pollution and CO removal efficiency. This provides a reference for the microalgal-based purification of actual domestic wastewater and raw biogas. PRACTITIONER POINTS: Nutrient and CO were efficiently removed by C. vulgaris with activated sludge. CO was removed up to 60.4% and was economically viable. Cocultivation of C. vulgaris and fungi could achieve the highest TN removal with WW4.
Co-pelletization of microalgae and fungi for efficient nutrient purification and biogas upgrading.
Zhao Yongjun,Guo Guangyong,Sun Shiqing,Hu Changwei,Liu Juan
The fungi-assisted microalgae pellets were cultivated to simultaneously purify biogas slurry and biogas. Results demonstrated that the optimized culture conditions for the pellets were at the shaking speed of 160 rpm, initial inoculum concentration of 1.0 × 10 spores L for microalgal cells, fungi/algae ratio of 1:10, mixed medium/simulated biogas slurry ratio of 3:7 incubated at a light intensity of 200 μmol m s. Moreover, biogas slurry purification and biogas upgrading were successfully achieved by co-cultivation of fungi-assisted microalgae pellets at mixed light wavelength of red:blue of 5:5. The highest removal efficiency of COD, TN, TP and CO were 92.17 ± 5.28%, 89.83 ± 4.36%, 90.31 ± 4.69% and 74.26 ± 3.14%, respectively. These results will provide a theoretical foundation for large-scale biogas slurry purification and biogas upgrading using fungi-assisted microalgal pellets.
Co-culturing microalgae with endophytic bacteria increases nutrient removal efficiency for biogas purification.
Xu Ming,Xue Zhaoxia,Sun Shiqing,Zhao Chunzhi,Liu Jinhua,Liu Juan,Zhao Yongjun
Endophytic bacteria were isolated from Chlorella vulgaris and co-cultured with its host microalgae to determine whether this symbiotic system is suitable for purifying biogas and biogas slurry. Results showed that endophytic bacteria S395-1 and S395-2 belonged to different genera. Both strains promoted microalgae growth while improving photosynthetic performance, carbonic anhydrase activity, nutrient removal efficiency, and CO fixation. The optimal bacteria (S395-2)-to-microalgae ratio and co-culture duration were 10:1 and 7 days. Under this condition, the growth rate and carbonic anhydrase activity were 0.196 ± 0.06 d and 31.24 ± 0.28 EU/cell, respectively. The symbiotic system had removal efficiencies of 88.29 ± 5.03%, 88.31 ± 4.29%, 88.21 ± 4.51%, and 68.13 ± 1.69% for chemical oxygen demand, nitrogen, phosphorus, and CO, respectively. These results will provide a framework for constructing a microalgal-bacterial consortium that can improve wastewater treatment and enhance biogas quality.
Induction of vitamin B12 to purify biogas slurry and upgrade biogas using co-culture of microalgae and fungi.
Xu Bing,Liu Jia,Zhao Chunzhi,Sun Shiqing,Xu Jie,Zhao Yongjun
Water environment research : a research publication of the Water Environment Federation
Different gradient concentrations of vitamin B12 (0 ng L , 10 ng L , 100 ng L , 1000 ng L ) were used in the symbiosis system (Chlorella vulgaris-Ganoderma lucidum or Chlorella vulgaris-Pleurotus ostreatus) to assess their effect on simultaneous purification of biogas and removal of nutrients in biogas slurry using co-culture of microalgae and fungi. When B12 was added to the symbiosis system, biomass growth, intracellular carbonic anhydrase activity (CA), chlorophyll-a content (CHL-a), photosynthetic characteristics of the two cultivation system, and removal efficiency of nutrients in biogas slurry and CO in biogas were significantly higher than those in the control group. The optimal concentration of B12 was determined to be 100 ng L considering the removal efficiency of nutrients and CO . Maximum mean chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and CO removal efficiencies were 75.98±6.26%, 78.46±6.21%, 80.21±6.83% and 61.08 ± 5.21% in Chlorella vulgaris-Ganoderma lucidum, respectively. This study showed the potential of microalgae and fungi symbiosis system with B12 addition for nutrient removal and biogas upgrading.