Abstract:In this work, the effect of zeolite montmorillonite KSF in the esterification of free fatty acids (FFAs) of crude African palm olein (Eleaias guinnesis Jacq) was studied. To optimize the esterification of FFAs of the crude African palm olein (CAPO), the response surface methodology (RSM) that was based on a central composite rotatable design (CCRD) was used. The effects of three parameters were investigated: (a) catalyst loading (2.6-9.4 wt %), (b) reaction temperature (133.2-166.2 • C), and (c) reaction time (0.32-3.68 h). The Analysis of variance (ANOVA) indicated that linear terms of catalyst loading (X 1 ), reaction temperature (X 2 ), the quadratic term of catalyst loading (X 2 1 ), temperature reaction (X 2 2 ), reaction time (X 2 3 ), the interaction catalyst loading with reaction time (X * 1 X 3 ), and the interaction reaction temperature with reaction time (X * 2 X 3 ) have a significant effect (p < 0.05 with a 95% confidence level) on Fatty Methyl Ester (FAME) yield. The result indicated that the optimum reaction conditions to esterification of FFAs were: catalyst loading 9.4 wt %, reaction temperature 155.5 • C, and 3.3 h for reaction time, respectively. Under these conditions, the numerical estimation of FAME yield was 91.81 wt %. This result was experimentally validated obtaining a difference of 1.7% FAME yield, with respect to simulated values.

SUMMARY Biofuels have been shown to be a promising and highly attractive alternative for minimizing the use of fossil fuels, and microalgae have positioned themselves as potential candidates for production of lipids and other substances of commercial interest. We briefly review recent advances made in microalgae culture conditions and genetic manipulation for improving lipid yields for biofuel production – with both approaches showing similar yields of triacylglycerides, indicating that more work is required for improving lipid yield and accumulation in algae. Aiming at gaining knowledge of algae genetic manipulation and exploring future use of this information for modifying the lipid biosynthesis pathway, we investigated whether some characteristics of enzymes involved in lipid biosynthesis could relate to lipid yield and accumulation in algae. We made an in silico analysis of amino acid sequence of enzymatic domains and modeled tertiary structure of three proteins involved in the biosynthesis of lipids in microalgae: acetyl‐CoA carboxylase, Acyl‐CoA: diacylglycerol acyltransferase, and glycerol‐3‐phosphate acyltransferase. Our results suggest that, based on primary amino acid sequences and tertiary structure of proteins shared by certain algae, it is likely that these proteins may relate to lipid yield and accumulation, which makes bioinformatics a powerful tool for in silico study of proteins and for selecting genes involved in lipid biosynthesis that could be useful for heterologous transformation in algae with the long term objective of improving their yield, accumulation, and fatty acid composition by genetic engineering.

How to cite this paper: Ramírez-Elías, M.A., Córdova-Quiroz, A.V., Cerón-Bretón, J.G., Cerón-Bretón, R.M., Rendón-von

In this study, African crude palm olein (CPO) was used to synthesize biodiesel. The objective was to determine the optimal reaction conditions for the methanolysis of olein. The used CPO had a 5.72% concentration of free fatty acids (FFA); thus, the production of biodiesel was carried out in two stages: 1) esterification using sulfuric acid and 2) transesterification using sodium methoxide. In order to optimize the yield of biodiesel during the transesterification process, a central rotatable design and the response surface methodology were used. The studied variables were: catalyst loading, reaction time and reaction temperature. The analysis of variance showed that the variables with significant effect were the catalyst loading, reaction temperature and reaction time; as well as the catalyst loading * reaction temperature and catalyst loading * reaction time. Results indicate that the optimal reaction conditions during transesterification are: 0.65% catalyst loading (wt/wtaceite), reaction time of 135 min and a reaction temperature of 56˚C. The optimal reaction conditions during esterification are: 2.5% weight of catalyst, reaction time of 150 min and a reaction temperature of 64.5˚C. Under these conditions, a 90% yield of biodiesel was obtained.

Microalgae have been positioned as excellent models for producing new sources of energy (biofuels and biohydrogen). Some investigations in these biological models have been directed to know if the enzymes ferredoxin (FDX) and hydrogenase (HYD) are involved in the algae producing different concentrations of molecular hydrogen (H 2 ). To date, little is known about the concomitant transcriptional regulation of both enzymes during H 2 evolution in algae. In this research, we evaluated the relative expression of hdy and fdx genes during the evolution of H 2 in three microalgae (Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii) in N-deprived anaerobic cultures in the presence of Fe, and 12:24 and 24:24 h dark:light cycles. We also detected structural differences in the enzymes. The 3D modeling indicated that the 3D structure of HYD and FDX are conserved in most algal genera, and the results of our grouping according to the aa characteristics of the proteins showed two grouping trends: One, according to the algae's phylogenetic classification, and another one according to the species-specific enzyme's characteristics, and the grouping could perhaps be more influenced by the algae's ability to produce H 2 . The three microalgae species reached maximum H 2 accumulation values in 24h:24 h dark:light conditions in Fe-supplemented media (4.2 AE 0.12 mL L À1 in C. vulgaris, 3.9 AE 0.10 mL L À1 in S. obliquus, and 4.5 AE 0.10 mL L À1 in C. reinhardtii), and the highest global relative expression of hyd and fdx genes was reached during the first hour of exposure to light, which suggests concomitant expression of both enzymes at the beginning of H 2 production. The behavior of the expression of the hyd and fdx genes in these algal species proved to be similar between species. A better understanding of the concomitant regulation of both enzymes could lay the groundwork for the future use of both enzymes to improve H 2 yields in microalgae.

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