High temperature alcoholic fermentation of orange peel by the newly isolated thermotolerant Pichia kudriavzevii KVMP10.

UNLABELLED: This work explores the potential for the development of orange peel based ethanol bioprocesses through isolation of the thermotolerant Pichia kudriavzevii KVMP10. A model solution of hydrolysed Valencia orange peel was employed to determine the ethanologenic potential of the yeast, which was maximized at 42°C producing 54 g l(-1) of ethanol. The effect of orange peel oil on bioethanol formation was investigated at 30 and 42°C confirming that the minimum inhibitory peel oil content was 0·01% (v/v). Pichia kudriavzevii KVMP10 demonstrated significant technological advantages for the production of sustainable bioenergy, such as utilization of both hexoses (glucose, sucrose, fructose and galactose) and pentoses (xylose) at high temperatures, exemplifying its great potential for application in orange peel based biorefineries for ethanol production. SIGNIFICANCE AND IMPACT OF THE STUDY: Citrus peel waste is one of the most underutilized and geographically diverse residues in the planet. In attempt to develop a citrus peel based biorefinery we report here the isolation of a yeast which exhibited favourable technological characteristics for the production of ethanol through utilization of the specific food waste. Pichia kudriavzevii KVMP10 was highly thermotolerant and utilized both hexoses and pentoses for ethanol production, which was achieved at elevated rates, highlighting its great potential for application in ethanol production processes from citrus peel.

The function of ORAOV1/LTO1, a gene that is overexpressed frequently in cancer: essential roles in the function and biogenesis of the ribosome.

ORAOV1 (oral cancer overexpressed) is overexpressed in many solid tumours, making a key contribution to the development of cancer, but the cellular role of ORAOV1 is unknown. The yeast orthologue of this protein is encoded by the hitherto uncharacterized essential gene, YNL260c. Expression of ORAOV1 restores viability to yeast cells lacking YNL260c. Under nonpermissive conditions, our conditional mutants of YNL260c are defective in the maturation of the 60S ribosomal subunit, whereas maturation of the 40S subunit is unaffected. Also, initiation of translation is abrogated when YNL260c function is lost. YNL260c is indispensible for life in oxygen, but is nonessential under anaerobic conditions. Consequently, the toxic affects of aerobic metabolism on biogenesis and function of the ribosome are alleviated by YNL260c, hence, we rename YNL260c as LTO1; required for biogenesis of the large ribosomal subunit and initiation of translation in oxygen. Lto1 is found in a complex with Rli1/ABCE1, an ATP-binding cassette (ABC)-ATPase bearing N-terminal [4Fe-4S] clusters. Like Lto1, the Rli1/ABCE1 [4Fe-4S] clusters are not required for viability under anaerobic conditions, but are essential in the presence of oxygen. Loss of Lto1 function renders cells susceptible to hydroperoxide pro-oxidants, though this type of sensitivity is specific to certain types of oxidative stress as the lto1 mutants are not sensitive to an agent that oxidizes thiols. These findings reflect a functional interaction between Lto1 and the Rli1/ABCE1 [4Fe-4S] clusters, as part of a complex, which relieves the toxic effects of reactive oxygen species (ROS) on biogenesis and function of the ribosome. This complex also includes Yae1, which bridges the interaction between Lto1 and Rli1/ABCE1. Interactions between members of this complex were demonstrated both in vivo and in vitro. An increased generation of ROS is a feature shared by many cancers. The ORAOV1 complex could prevent ROS-induced ribosomal damage, explaining why overexpression of ORAOV1 is so common in solid tumours.

Fouling cake layer in a submerged anaerobic membrane bioreactor treating saline wastewaters: curse or a blessing?

The treatment of inhibitory (saline) wastewaters is known to produce considerable amounts of soluble microbial products (SMPs), and this has been implicated in membrane fouling; the fate of these SMPs was of considerable interest in this work. This study also investigated the contribution of SMPs to membrane fouling of the; (a) cake layer/biofilm layer, (b) the compounds below the biofilm/cake layer and strongly attached to the surface of the membrane, (c) the compounds in the inner pores of the membrane, and (d) the membrane. It was found that the cake/biofilm layer was the main reason for fouling of the membrane. Interestingly, the bacteria attached to the cake/biofilm layer showed higher biodegradation rates compared with the bacteria in suspension. Moreover, the bacteria attached to the cake layer showed higher amounts of attached extracellular polysaccharides (EPS) compared with the bacteria in suspension, possibly due to accumulation of the released EPS from suspended biomass in the cake/biofilm layer. Molecular weight (MW) analysis of the effluent and reactor bulk showed that the cake layer can retain a large fraction of the SMPs in the reactor and prevent them from being released into the effluent. Hence, while cake layers lead to lower fluxes in submerged anaerobic membrane bioreactors (SAMBRS), and hence higher costs, they can improve the quality of the reactor effluent.

Are compatible solutes compatible with biological treatment of saline wastewater? Batch and continuous studies using submerged anaerobic membrane bioreactors (SAMBRs).

This study investigated fundamental mechanisms that anaerobic biomass employ to cope with salinity, and applied these findings to a continuous SAMBR. When anaerobic biomass was exposed to 20 and 40 g NaCl/L for 96 h, the main solute generated de novo by biomass was trehalose. When we separately introduced trehalose, N-acetyl-ß-lysine and potassium into a batch culture a slight decrease in sodium inhibition was observed. In contrast, the addition of 0.1 mM and 1 mM of glycine betaine dramatically improved the adaptation of anaerobic biomass to 35 g NaCl/L, and it continued to enhance the adaptation of biomass to the salt for the next three batch feedings without further addition. No shift in archaeal microbial diversity was found when anaerobic biomass was exposed in batch mode to 35 g NaCl/L for 360 h, and no changes were found when glycine betaine was added. The dominant species identified under these conditions were Methanosarcina mazeii and Methanosaeta sp. The addition of 5 mM glycine betaine to a continuous SAMBR at 12 h hydraulic retention time (HRT), and operation in batch mode for 2 days can significantly enhance saline (35 g NaCl/L) synthetic sewage degradation. In addition, the injection of 1 mM of glycine betaine into a SAMBR for five subsequent days also significantly enhanced dissolved organic carbon (DOC) removal from sewage under these conditions. The main compatible solutes generated by anaerobic biomass after 44 days exposure to 35 g NaCl/L in a SAMBR were N-acetyl-ß-lysine and glycine betaine. Finally, the addition of 1 mM glycine betaine to the medium was beneficial for anaerobic biomass in batch mode at 20 °C under saline and non saline conditions.

Post-treatment of a submerged anaerobic membrane bioreactor (SAMBR) saline effluent using powdered activated carbon (PAC).

Powdered activated carbon (PAC) was added to an effluent from a submerged anaerobic membrane bioreactor (SAMBR) treating saline wastewater as a post-treatment method. The adsorption of contaminants was carried out and key Freundlich isotherm parameters were evaluated. The results showed a reduction in dissolved organic carbon (DOC) in the effluent of over 80% after treatment with 1.7gPAC/L. The composition of the effluent was determined by the use of size exclusion chromatography (SEC) and by GC-MS analysis. Most of the components of the effluent had a MW less than 1 kDa, and these were the hardest to eliminate by PAC adsorption. m-Aminophenylacetylene, cyclohexane 1,2,4 trimethyl and cholestan 3-one were found in the effluent, but could be removed by PAC adsorption. Finally, different methods for using PAC, with or without biomass, revealed that aerobic biomass enhanced the adsorption process resulting in higher DOC removals.

Saline sewage treatment using a submerged anaerobic membrane reactor (SAMBR): effects of activated carbon addition and biogas-sparging time.

This study investigated the performance of a submerged anaerobic membrane reactor (SAMBR) treating saline sewage under fluctuating concentrations of salinity (0-35g NaCl/L), at 8 and 20h HRT, with fluxes ranging from 5-8litres per square metre per hour (LMH). The SAMBRs attained a 99% removal of Dissolved Organic Carbon (DOC) with 35g NaCl/L, while removal inside the reactor was significantly lower (40-60% DOC). Even with a sudden drop in salinity overall removal recovered quickly, while the recovery inside the reactor took place at a slower rate. This highlights the positive effect of the membrane in preventing the presence of high molecular weight organics in the effluent while also retaining biomass inside the reactor so that they can rapidly acclimatize to salinity. The reduction of continuous biogas sparging to intervals of 10min ON and 5min OFF resulted in a slight increase in transmembrane pressure (TMP) by 0.025bar, but also resulted in an increase in effluent DOC removal and inside the SAMBR by 10% and 20%, respectively. The addition of powdered activated carbon (PAC) resulted in a decrease in the TMP by 0.070bar, and an increase in DOC removal in the reactor and effluent by 30% and 5%, respectively. The PAC dramatically decreased the high molecular weight organics in the reactor over a period of 72h. SEM pictures of the membrane and biomass before and after addition of PAC revealed a remarkable reduction of flocks on the membrane surface, and a reduction inside the reactor of soluble microbial products (SMPs). Finally, Energy Dispersive X-ray (EDX) analysis of the membranes pores and biofilm highlighted the absence of organic matter in the inner pores of the membrane.

A modified method for the determination of chemical oxygen demand (COD) for samples with high salinity and low organics.

This study proposes a modification to the standard method for the determination of the chemical oxygen demand of samples with a salinity up to 40 g NaCl/L and low organic concentrations (20-230 mg COD/L). The masking of chloride by the use of a HgSO(4):Cl ratio of 20:1 prior to digestion, and the use of 3g K(2)Cr(2)O(7)/L in the digestion solution resulted in an error of less than 10% and 12% for samples containing 40 g NaCl/L at 20-190 mg COD/L and 230 mg COD/L, respectively. Comparison of the standard method with the new proposed method using a synthetic sewage highlights the large errors (50-85%) of the standard method in contrast to an error of less than 10% for the proposed modified method.

Effect of fluctuations in salinity on anaerobic biomass and production of soluble microbial products (SMP(s)).

This study investigated the acclimation potential of batch fed anaerobic biomass with salinities of 0-50 gNaCl l(-1). Anaerobic biomass was acclimatized to salinities up to 20 gNaCl l(-1)over a period of 35 days, with 3 consecutive feedings. After this period the biomass was subjected to non-saline conditions to simulate fluctuating feed compositions. High activity was obtained after the first exposure to non saline conditions for biomass previously exposed to 30 gNaCl l(-1). Short exposure (2-48 h) to high salinity (40 gNaCl l(-1)) did not reduce biomass activity when it was re-subjected to normal conditions. The sensitivity of each anaerobic bacterial group showed that propionate utilisers were the most affected by sudden changes in salinity. Using size exclusion chromatography (SEC) it was found that biomass exposed to concentrations of salinity above 30 gNaCl(-1) produced higher molecular weight soluble microbial products (SMPs) which were present in the culture for longer periods than the control indicating that the effluent was more difficult to degrade. With the sudden removal of salinity anaerobic biomass can easily readapt to normal conditions without any high MW compounds being produced. These findings highlight the fact that anaerobic biomass is able to overcome sharp decreases in salinity in contrast with aerobic biomass as reported in the literature.