Effect of initial pH and substrate concentration on the lactic acid production from cassava wastewater fermentation by an enriched culture of acidogenic microorganisms.

Recently, cassava processing wastewater has been considered an alternative substrate for lactic acid production due to its appreciable carbohydrate levels. The authors carried out different batch reactor trials aiming to favor the production of lactic acid through the fermentation of non-sterilized cassava wastewater by an enriched culture of acidogenic microorganisms. To this end, the impact of different initial pHs (4.5, 5.0, 5.7, 6.5, and 7.0) and different initial substrate concentrations (10, 15.8, 30, 44.2, and 50 g/L) in terms of glucose on lactic acid production yield (Y) was evaluated by applying the design of experiment (DoE) known as central composite rotatable design (CCRD). The highest rate of lactic acid production (40 g/L) occurred with an initial pH of 6.5 and an initial substrate concentration of 50 g/L. The maximum yield was higher in trials T1, T2, T4, T5, and T8, reaching values of 0.80, 0.62, 0.60, 0.96, and 0.70 g/g, respectively. The maximum lactic acid productivity (P), of 0.60 and 0.73 g L-1  hr-1 , was observed in trials T5 and T8, respectively. The enriched culture of acidogenic microorganisms was shown to favor the production of lactic acid, since the production of other acids, such as acetic and propionic acid, did not exceed 3.5 and 4.5 g/L, respectively. © 2020 Water Environment Federation PRACTITIONER POINTS: Cassava wastewater presented potential to lactic acid production. The CCRD showed that highest lactic acid concentrations (40 g/L). The adoption of cassava wastewater or manipueira as a substrate resulted in important information on the tendency to obtain value-added products such as lactic acid.

Genome-wide sequencing and metabolic annotation of Pythium irregulare CBS 494.86: understanding Eicosapentaenoic acid production.

BACKGROUND: Pythium irregulare is an oleaginous Oomycete able to accumulate large amounts of lipids, including Eicosapentaenoic acid (EPA). EPA is an important and expensive dietary supplement with a promising and very competitive market, which is dependent on fish-oil extraction. This has prompted several research groups to study biotechnological routes to obtain specific fatty acids rather than a mixture of various lipids. Moreover, microorganisms can use low cost carbon sources for lipid production, thus reducing production costs. Previous studies have highlighted the production of EPA by P. irregulare, exploiting diverse low cost carbon sources that are produced in large amounts, such as vinasse, glycerol, and food wastewater. However, there is still a lack of knowledge about its biosynthetic pathways, because no functional annotation of any Pythium sp. exists yet. The goal of this work was to identify key genes and pathways related to EPA biosynthesis, in P. irregulare CBS 494.86, by sequencing and performing an unprecedented annotation of its genome, considering the possibility of using wastewater as a carbon source. RESULTS: Genome sequencing provided 17,727 candidate genes, with 3809 of them associated with enzyme code and 945 with membrane transporter proteins. The functional annotation was compared with curated information of oleaginous organisms, understanding amino acids and fatty acids production, and consumption of carbon and nitrogen sources, present in the wastewater. The main features include the presence of genes related to the consumption of several sugars and candidate genes of unsaturated fatty acids production. CONCLUSIONS: The whole metabolic genome presented, which is an unprecedented reconstruction of P. irregulare CBS 494.86, shows its potential to produce value-added products, in special EPA, for food and pharmaceutical industries, moreover it infers metabolic capabilities of the microorganism by incorporating information obtained from literature and genomic data, supplying information of great importance to future work.