RESUMEN
Aims: Efficient utilization of cassava waste for value addition depends largely on proper understanding of its true microbial diversity. The aim of this study was to characterize using molecular methods, fungal species associated with cassava waste and to highlight their industrial potential. Study Design: Cassava peel (CP) waste from CP waste dumpsites and cassava waste water from cassava wastewater discharge outlets were collected from major cassava processing centres in Abeokuta, Ogun State, Nigeria, for the study. Place and Duration of Study: Biotechnology Centre, Federal University of Agriculture, Abeokuta, Ogun State, Nigeria; between June 2011 and March 2012. Methodology: Two molecular methods namely, total fungal community DNA and isolates DNA sequence analysis were employed to characterize and identify the fungal species. Total fungal community DNA was extracted directly from CP waste and cassava wastewater, using the Soil DNA isolation kit (Norgen, Canada), while total genomic DNA was extracted from fungal isolates, using the same kit. The fungal ITS2 (Internal transcribed spacer) gene sequence of total fungal community and genomic DNA was amplified by Polymerase Chain Reaction (PCR) using ITS2 primers. Total fungal community DNA amplicons were spliced into PCR-TRAP Cloning Vector, used to transform competent cells of Escherichia coli and sequenced. Sequences were identified by aligning with sequences in the GenBank. Results: Results showed that 17 fungal species including Eurotiomycetes – Eurotiales (6 species), Mucormycotina – Mucorales (1 species), Sordariomycetes - Hypocreales (1 species), Saccharomycetes Saccharomycetales (8 species), and unidentified fungi (1 species) were present in cassava peel (CP). The dominant species was Aspergillus niger (15.2%). However, cassava wastewater had 27 fungal species including Eurotiomycetes – Eurotiales (2 species), Saccharomycetes Saccharomycetales (24 species) Tremellomycetes-Tremellales (1 species); the dominant species being Saccharomyces cerevisiae and Candida krusei each with 8.7% relative abundance. Conclusion: This study shows that cassava waste, on account of its rich fungal diversity, is an important microbial resource.
RESUMEN
background: Lactic acid (LA) is a carboxylic acid widely used as preservative, acidulant, and/or flavouring in food industry; it is also used as a raw material for the production of lactate ester, propylene glycol, 2,3-pentanedione, propanoic acid, acrylic acid and acetaldehyde. In recent years, the demand for LA production has dramatically increased due to its application as a monomer for poly-lactic acid synthesis, a biodegradable polymer used as a plastic in many industrial applications. LA can be produced either by fermentation or chemical synthesis; the former route has received considerable interest, due to environmental concerns and the limited nature of petrochemical feedstocks; thus, 90% of LA produced worldwide is obtained by fermentation, this process comprises the bioconversion of a sugar solution (carbohydrates) into LA in the presence of a microorganism. Objectives: This work is aimed at studying the effect of pH control and culture media composition on the LA production using renewable sources from the agroindustry sector. Methods: A Lactobacillus brevis strain is used to perform lab scale experiments under aerobic and anaerobic conditions, using three different culture media compositions: a high nutritional content medium (MRS), as a reference, a low nutritional content medium with glucose as the only carbon source (GM), and a potential low nutritional content medium with cassava flour as carbon source (HY1). results: The higher LA production is accomplished under anaerobic conditions, 17.6 ± 0.1, 12.6 ± 0.2 y 13.6 ± 0.2 g LA/L, for MRS, GM and HY1 medium, respectively. The effect of pH on LA biosynthesis in a 5L bioreactor is also studied using the HY1 medium. For a fermentation time of 120 h, the highest LA concentration obtained was 24.3 ± 0.7g LA/L, productivity 0.20 g/L/h, YP/S 0.32g LA/g syrup, at pH 6.5...