Steam Explosion (STEX) of Citrus × Poncirus Hybrids with Exceptional Tolerance to Candidatus Liberibacter Asiaticus (CLas) as Useful Sources of Volatiles and Other Commercial Products

Florida citrus production has declined 75% due to Huanglongbing (HLB), a disease caused by the pathogenic bacterium Candidatus Liberibacter asiaticus (CLas). Methods to combat CLas are costly and only partially effective. The cross-compatible species Poncirus trifoliata and some of its hybrids are known to be highly tolerant to CLas, and thus can potentially serve as an alternative feedstock for many citrus products. To further investigate the commercial potential of citrus hybrids, three citrus hybrids, US-802, US-897, and US-942, were studied for their potential as feedstocks for citrus co-products using steam explosion (STEX) followed by water extraction. Up to 93% of sugars were recovered. US-897 and US-942 have similar volatile profiles to that of the commercial citrus fruit types and as much as 85% of these volatiles could be recovered. Approximately 80% of the pectic hydrocolloids present in all three hybrids could be obtained in water washes of STEX material. Of the phenolics identified, the flavanone glycosides, i.e., naringin, neohesperidin, and poncirin were the most abundant quantitatively in these hybrids. The ability to extract a large percentage of these compounds, along with their inherent values, make US-802, US-897, and US-942 potentially viable feedstock sources for citrus co-products in the current HLB-blighted environment.

Enhanced glyoxylate shunt for efficient production of C4 derivatives using fatty acids feedstocks

Biosynthesis of TCA cycle-derived C4 chemicals through glyoxylate shunt is an attractive metabolic route because it can be drived by TCA-glyoxylate cycle force under aerobic conditions. However, yield of this route is low with at least 1/3 carbon loss from glucose. FAs could sufficiently provide acetyl-CoA by β-oxidation without carbon loss and directly enter the TCA-glyoxylate cycle, which is acknowledged as a promising alternative feedstock. Here β-alanine was selected as the target TCA cycle-derived chemical, of which the theoretical yield is 1.391 g/g FAs, much higher than that of glucose(0.49 g/g). By adopting multi-metabolic engineering strategies and relieving the active oxygen damage caused by FAs utilization, β-alanine production reached 78.05 g/L with a yield of 1.2 g/g, about 86% of theoretical yield. Our study establish a promising bioproduction route of β-alanine from waste FAs (such as gutter oil, palm fatty acid distillate etc.), and more importantly, provide an efficient platform for TCA cycle-derived C4 chemicals biosynthesis.

Bacterial alginate metabolism: an important pathway for bioconversion of brown algae

Brown macroalgae have attracted great attention as an alternative feedstock for biorefining. Although direct conversion of ethanol from alginates (major components of brown macroalgae cell walls) is not amenable for industrial production, significant progress has been made not only on enzymes involved in alginate degradation, but also on metabolic pathways for biorefining at the laboratory level. In this article, we summarise recent advances on four aspects: alginate, alginate lyases, different alginate-degrading systems, and application of alginate lyases and associated pathways. This knowledge will likely inspire sustainable solutions for further application of both alginate lyases and their associated pathways.

New non-edible Allanblackia parviflora seed oil as an alternative feedstock for biodiesel production and characterization of the fuel

This study is aimed at producing biodiesel from Allanblackia parviflora seed oil as a new non-edible alternative resource. The amount of oil extracted from the seeds was approximately 49% and was mainly composed of linoleic acids (66.68). The Allanblackia parviflora methyl esters (APME) were prepared using NaOH as a homogeneous base-catalyst for the transesterification. The rate of conversion of the triglycerides to methyl esters was determined using Gas Chromatograph with an optimum yield of 97.1%. The conditions under which this maximum yield (97.1%) was obtained include methanol to Allanblackia parviflora oil ratio of 6:1, reaction temperature of 60 ℃, NaOH concentration of 1% and reaction time of 2 h. The properties of the methyl esters were comparable to fuel properties of conventional diesel using ASTM and European Union standards. The seeds of Allanblackia parviflora can be described as promising non-edible resource.

Pressurized Steam Conversion of Biomass Residues for Liquid Hydrocarbons Generation

Biomass residues are often considered as a resource if conveniently converted in fuel and alternative feedstock for chemical processes, and their conversion into valuable products may occur by different pathways. This work is focused on the thermochemical conversion at moderate temperature and in steam atmosphere, a mild process in comparison to hydrothermal liquefaction, followed by extraction of soluble products in a solvent. Such process has been already applied to various residues and here extended to the case of marc, the residual pomace from wine making, largely produced worldwide. A pressurized batch reactor was used for the quantitative determination of produced solid and liquid fractions, and their qualitative characterization was performed by instrumental analyses. The pressurized steam conversion of marc was effective, providing a yield in liquid fraction, upon extraction in solvent, up to 30% of the raw dried biomass. The use of polar and nonpolar solvent for the extraction of the liquid fraction was inspected. Applied operating conditions, namely residence time in the batch reactor and extraction modality, showed a significant influence on the process performance. In particular, long residence and extraction times and use of nonpolar solvent substantially improved the yield in liquid fraction.

Fast Synthesis of Hydroxymethylfurfural from Levoglucosenone by Mixing with Sulphuric Acid and Heating in a Microtube Reactor

Hydroxymethylfurfural (HMF) is a promising platform chemical in future bio-based chemical industry for synthesis of a variety of furan derivatives. Studies on the HMF synthesis have focused mainly on saccharides as the feedstock. Recently, levoglucosenone (LGO), anhydrosugar available from cellulose pyrolysis, has been identified as an alternative feedstock, which can be converted to HMF under milder conditions only with acid and water as catalyst and solvent, respectively. To further explore the potential of this reaction, in this study, we demonstrated the HMF synthesis below 100°C within a few minutes at high yields. The employment of microtube reactor and high concentration sulfuric acid as catalyst was effective, leading to the highest HMF yield of 61.5%-C with the reaction selectivity over 80%. Kinetic analysis revealed that rapid heating after mixing LGO with the catalytic aqueous solution was essential to supress side reaction that generates degradation products from LGO. The reaction with glucose or fructose as feedstock under same conditions resulted in poor HMF yield.

Lignin Promoted the Fast Formation of Robust and Highly Conductive Deep Eutectic Solvent Ionic Gel at Room Temperature for Flexible Quasi-Solid-State Supercapacitor and Strain Sensors

Green synthesis of ionic gel with alternative feedstock provides possible to prepare sustainable materials and devices. Due to the excellent solubility of lignin in deep eutectic solvent (DES), lignin was...

Microalgae Growth and Phosphorus Uptake of Chlamydomonas Reinhardtii 11/32C under Different Inorganic Nitrogen Sources

Microalgae have been proven to be effective in utilizing nitrogen (N) and phosphorus (P) from a wide range of wastewater sources. This ability enhances the potential role that microalgae may have not only in wastewater bioremediation, but also in algal biomass production as an alternative feedstock for biodiesel and bio-fertilizer production. To investigate the ability of microalgae at recovering nutrients, the microalga strain Chlamydomonas reinhardtii 11/32C was selected to determine P uptake rates. Results shown that C.reinhardtii 32C cultivated in combination of NO3- and NH4+ as nitrogen sources was able to uptake 0.067 mg P l-1d-1. Combination of both nitrogen can produce specific growth rate of 0.128 d-1 and 89 mg VSS l-1d-1 of biomass dry weight. These value is the highest compare to C.reinhardtii 32C cultivated in NO3- or NH4+. These findings are fundamental to understand and plan future studies for cultivation conditions to induce luxury nutrient uptake by selected microalga.

UV Mutagenesis as a Strategy to Enhance Growth and Lipid Productivity of Chlorella sp. 042

Microalgae appeared to be an alternative feedstock for renewable biodiesel production due to their capability to accumulate considerable amounts of lipids. In this study, mutagenesis using UVC light with different periods was applied to Chlorella sp. 042 to produce a microalgae strain with high lipid productivity of 45, 60, and 75 min. The Nile red fluorescence method was conducted to select a Chlorella sp. mutant with high neutral lipid and generated one mutant from every UV mutation period, M45-06, M60-02, and M75-21. All of the mutants have higher growth rates than the wild type. Chlorella sp. 042 M60-02 achieved the highest lipid productivity, with 34 mg L-1 day-1. Furthermore, as other major biochemical components, carbohydrate and protein contents were determined. Our results showed that all the mutants enhance their carbohydrate and protein contents compared to the wild type. However, mutations for more than 60 min do not intensely change the protein content of mutant microalgae. Gas chromatography-mass spectrophotometry analysis revealed that M60-02 mutant has similar FAME profiles with the wild type, which contain palmitic acid (C16:0), stearic acid (C 18:0), oleic acid (C18:1), and linoleic acid (C18:2). These results demonstrate that the UV mutation of Chlorella sp. 042 for 60 min is suitable as a source of biodiesel production.