Waste-to-energy nexus: A sustainable development.

http://repositorium.sdum.uminho.pt/bitstream/1822/64131/1/document_52293_1.pdf

Recent trends on seaweed fractionation for liquid biofuels production.

In order to combat emerging concerns due to global climate change and increasing conventional fuel prices, bioethanol appears to be a sustainable green resource as co-fuel to meet the future energy demand for transportation. As per the present scenario, bioenergy research emphasizes on bioethanol production from alternate non-terrestrial substrates, like microalgae and macroalgae. Among them, macroalgae represent a rich source of carbohydrates for bioethanol production. The production of bioethanol from macroalgal biomass mainly involves three steps namely mechanical pre-processing, pretreatment and microbial fermentation. Of these, the pretreatment step is the most crucial that tends to improve the saccharification efficiency for efficient bioethanol production. Currently, there are three main types of pretreatment methods used for macroalgae viz., physical/physicochemical, chemical and biological. In addition, the two-step saccharification or combinational pretreatment approach is also utilized to enhance the yield of reducing sugars, which can be fermented to bioethanol using suitable microbial strain(s) under restrained conditions. The current review provides a critical assessment and detailed overview about the sequential process for bioethanol production from macroalgal biomass. Additionally, this paper gives an insight on various statistical optimization approaches using response surface methodology for the biomass pretreatment step and provides a viewpoint about the technical advances in third-generation bioethanol production.

A critical review on production of bioethanol from macroalgal biomass

Ulva lactuca is a green macro alga involved in devastating green tides observed worldwide. These green tides or blooms are a consequence of human activities. Ulva blooms occur mainly in shallow waters and the decomposition of this alga can produce dangerous vapors. Ulva lactuca is a species usually resembling lettuce, but genetic analyses demonstrated that other green algae with tubular phenotypes were U. lactuca clades although previously described as different species or even genera. The capacity for U. lactuca to adopt different phenotypes can be due to environment parameters, such as the degree of water salinity or symbiosis with bacteria. No efficient ways have been discovered to control these green tides, but the Mediterranean seas appear to be protected from blooms, which disappear rapidly in springtime. Ulva contains commercially valuable components, such as bioactive compounds, food or biofuel. The biomass due to this alga collected on beaches every year is beginning to be valorized to produce valuable compounds. This review describes different processes and strategies developed to extract these different valuable components.

https://hal.archives-ouvertes.fr/hal-02160426/document

Ulva lactuca, A Source of Troubles and Potential Riches.

The rapid depletion and environmental concerns associated with the use of fossil fuels has led to extensive development of biofuels such as bioethanol from seaweeds. The long-term prospect of seaweed bioethanol production however, depends on the selection of processes in the hydrolysis and fermentation stages due to their limiting effect on ethanol yield. This review explored the factors influencing the hydrolysis and fermentation stages of seaweed bioethanol production with emphasis on process efficiency and sustainable application. Seaweed carbohydrate contents which are most critical for ethanol production substrate selection were 52 ± 6%, 55 ± 12% and 57 ± 13% for green, brown and red seaweeds, respectively. Inhibitor formation and polysaccharide selectivity were found to be the major bottlenecks influencing the efficiency of dilute acid and enzymatic hydrolysis, respectively. Current enzyme preparations used, were developed for starch-based and lignocellulosic biomass but not seaweeds, which differs in polysaccharide composition and structure. Also, the identification of fermenting organisms capable of converting the heterogeneous monomeric sugars in seaweeds is the major factor limiting ethanol yield during the fermentation stage and not the SHF or SSF pathway selection. This has resulted in variations in bioethanol yields, ranging from 0.04 g/g DM to 0.43 g/g DM.

https://backend.orbit.dtu.dk/ws/files/175708001/fermentation_04_00099.pdf

Seaweed Bioethanol Production: A Process Selection Review on Hydrolysis and Fermentation

Optimization of thermal acid hydrolysis for bioethanol production from Ulva rigida with yeast Pachysolen tannophilus

Chemical diversity of essential oil of the Moroccan endemic Origanum grosii in natural populations and after transplantation

We investigated the in vitro effect of the use of Ulva rigida extract as a plant stimulant on carob root induction. Treatments at different concentrations of U. rigida extract were tested, as well as treatment by immersion of the basal portion of the hypocotylar sections in a solution of indole-3-butyric acid (IBA) before their cultivation in agar medium contains seaweed extract have been tested. The results showed that the application of U. rigida significantly increased the growth and rooting of carob cuttings. Plants treated with U. rigida extract outperformed the untreated plants in terms of plant height, number of internodes, number of leaves, number of roots, and root length with a high percentage of rooting of 83%. The higher response in the adventitious roots of carob hypocotyl cuttings was recorded with a treatment combination with IBA at a concentration of 2 mgL -1 and culturing in a medium containing 4% U. rigida extract. The results demonstrate a significant effect of U. rigida extracts on the root development of Ceratonia siliqua . This study highlights the possibility of developing procedures to improve the rooting capacity of recalcitrant plants while improving their growing environment.

N. El Mtili

Papers

Optimization of thermal acid hydrolysis for bioethanol production from Ulva rigida with yeast Pachysolen tannophilus

Chemical diversity of essential oil of the Moroccan endemic Origanum grosii in natural populations and after transplantation

Effect of liquid seaweed (Ulva rigida) extract on the growth and rooting of carob (Ceratonia siliqua L.)