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In the present study, the mixotrophic growth of the microalga Nannochloropsis sp. BR2 in sugarcane bagasse was analyzed and compared with its photoautotrophic cultivation. Nannochloropsis cultures cultivated mixotrophically in sugarcane bagasse showed significantly higher biomass productivity, fatty acid methyl ester (FAME) and protein contents of 63.28 mg L−1 d−1, 170.51 mg g−1 and 35.2% of dry weight, respectively, compared to the photoautotrophic cultivations with biomass productivity, FAME and protein contents of 51 mg L−1 d−1, 139.21 mg g−1 and 31.6% of dry weight. Whereas, total carotenoid during photoautotrophic cultivation was 5.833 mg g−1 and decreased to 4.542 mg g−1 in mixotrophic cultures. This can be explained by the additional carbon source in the form of sugars that are metabolized to the fatty acid building block acetyl-CoA, while photosynthetic pigments were less needed. Findings of this study demonstrate that acid-pretreated hydrolysate of lignocellulosic waste from sugarcane bagasse can be developed into a potential feedstock for efficient microalgal cultivation.

Today, global focus of research is to explore the solution of energy crisis and environmental pollution. Like other agricultural countries, bulk quantities of watermelon peels (WMP) are disposed-off in environment as waste in Pakistan and appropriate management of this waste is the need of hour to save environment from pollution. The work emphasizes the role of ethanologenic yeasts to utilize significant sugars present in WMP for low-cost bioethanol fermentation. Dilute hydrochloric acid hydrolysis of WMP was carried out on optimized conditions employing RSM (response surface methodology) following central composite design (CCD). This experimental design is based on optimization of ethanologenesis involving some key independent parameters such as WMP hydrolysate and synthetic media ratio (X1), incubation temperature (X2) and incubation temperature (X3) for maximal ethanol yield exploiting standard (Saccharomyces cerevisiae K7) as well as experimental (Metchnikowia cibodasensisY34) yeasts. The results revealed that maximal ethanol yields obtained from S. cerevisiae K7 was 0.36±0.02 g/g of reducing sugars whereas M. cibodasensisY34, yielded 0.40±0.01 g ethanol/g of reducing sugars. The yeast isolate M. cibodasensisY34 appeared as promising ethanologen and embodies prospective potential for fermentative valorization of WMP-to-bioethanol. Resumo Hoje, o foco global da pesquisa é explorar a solução da crise energética e da poluição ambiental. Como em outros países agrícolas, grandes quantidades de cascas de melancia (WMP) são descartadas como resíduos no meio ambiente no Paquistão, mas a gestão adequada desses resíduos é a mais recente solução para salvar o meio ambiente da poluição. O trabalho enfatiza o papel das leveduras etanologênicas para utilizar açúcares significativos presentes no WMP para fermentação de bioetanol de baixo custo. A hidrólise de ácido clorídrico diluído de WMP foi realizada em condições otimizadas empregando RSM (metodologia de superfície de resposta) e seguindo o projeto de composto central (CCD). Este projeto experimental é baseado na otimização da etanologenesis envolvendo alguns parâmetros independentes importantes, como hidrolisado de WMP e razão de meio sintético (X1), temperatura de incubação (X2) e temperatura de incubação (X3) para rendimento máximo de etanol explorando o padrão (Saccharomyces cerevisiae K7) também como leveduras experimentais (Metchnikowia cibodasensis Y34). Os resultados revelaram que os rendimentos máximos de etanol obtidos a partir de S. cerevisiae K7 foi de 0,36 ± 0,02 g / g de açúcares redutores, enquanto M. cibodasensis Y34 rendeu 0,40 ± 0,01 g de etanol / g de açúcares redutores. O isolado de levedura M. cibodasensis Y34 apareceu como um etanologeno promissor e incorpora um potencial prospectivo para a valorização fermentativa de WMP em bioetanol.

Overuse of the fossil fuels to fulfill existing energy requirements has generated various environmental problems like global warming. Emergence of environmental issues due to burning of the fossil fuel resources has provoked researchers to explore alternative sources of fuel. In this scenario, microalgal biofuels could present a promising alternative fuel if produced cost-effectively without competing for freshwater resources and arable land. Aim of the present study was to grow microalgae by employing lignocellulosic waste for production of lipids. Scenedesmus dimorphus NT8c was chosen based on its ability to tolerate heat, rapid growth, and ease of harvesting by overnight settling. Biochemical composition and growth parameters of microalgae were analyzed when cultivated mixotrophically on sugarcane bagasse hydrolysate, a low-value agricultural by-product, that is, currently underutilized. Despite a slight increase in turbidity in the medium, S. dimorphus NT8c cultures raised mixotrophically in 5 g/L sugarcane bagasse hydrolysate displayed significantly higher growth rates compared to photoautotrophic cultivation with an overall biomass productivity of 119.5 mg L d, protein contents of 34.82% and fatty acid contents of 15.41%. Thus, microalgae cultivated mixotrophically are capable of photosynthesizing while metabolizing and assimilating organic carbon, significant increases of biomass and lipid productivity can be achieved. However, high supplementation with organic carbon can result in unfavorable levels of turbidity and bacterial growth, reducing microalgal biomass productivity.

Phenotypic characteristics while complimenting 16S rRNA gene sequencing in identifying bacteria become decisive in solving conflicts of equal % similarity of a given DNA sequence to more than one classified microorganisms. "Phenotypic light" may also indicate right direction when a new species' 16S rDNA sequence is under consideration. In fact 16S rRNA gene sequences give indication that either a novel species has been isolated or the test organism is identified. In each case additional tests are required for resolving different issues. Predictions of microbial phenotypes from metagenomic data depend heavily on our knowledge of expressed genes. Thus renaissance of microbial phenotypic characterization is likely to emerge at par with genotypic signatures. Interplay of these and other complimentary levels of analyses are likely to lead DNA barcoding for microorganisms as it has provided efficient methods for species-level identifications of animals and plants. In this review, an attempt has been made to realize the reader(s) importance of interplay of genotypic and phenotypic characteristics of bacteria for development of comprehensive and more stable classification schemes. It is expected that future valid classification schemes will be based on the phenetic relationships of microorganisms.