ANTIBACTERIAL EFFECT OF NANNOCHLOROPSIS OCULATA AS ROOT CANAL STERILIZATION MATERIAL ON STREPTOCOCCUS MUTANS BIOFILM

ABSTRACTBackground: Streptococcus mutans in the most frequent microbiota that causes pulp necrosis because of caries. The microorganism that is colonized and embedded in the biofilm matrix is resistant to antimicrobials compared to planktonic cells. Root canal sterilization materials must have good biocompatibility with tissues. Nannochloropsis oculata is an algae that contains various compounds such as terpenoids, alkaloids, and flavonoids that have potential as antibacterial and antioxidant and can be used as alternative to root canal sterilization. Method: This research was true experimental laboratory research with post-test only control group design. The antibacterial potential of Nannochloropsis oculata was tested using the biofilm method, divided into 5 groups. The control group was: K- (aquadest), K+ (calcium hydroxide), and the treatment group was given Nannochloropsis oculata: P1 (0.625%), P2 (1.25%), and P3 (2.5 %). Congo Red method test was to determine the formation of biofilm that shows black strains on agar. While biofilm test with Microtiter Plate Assay to measure the value of biofilm that were inhibited in Optical Density (OD) value in the ELISA Reader. The lower the value, the more biofilm inhibited, with OD value, inhibition percentage could counted Result: The result of all treatment groups were increasing in percentage inhibition value shows inhibition in biofilm growth (p <0.05). Conclusion: Nannochloropsis oculata had an antibacterial effect on the biofilm of Streptococcus mutans

Toxicity Mechanisms of ZnO Nanoparticles in Nanochloropsis Oculata with a Comparative Approach with CuO and Ag Nanoparticles

The purpose of present work was the investigation of different concentrations of zinc oxide nanoparticles on the marine microalga Nannochloropsis oculata and compare the results of this study with previous studies. Dissolution of ZnO NPs in nanopure water was 0.378-3.12 mg/L and the rate solubility decreased with increasing the concentrations of ZnO NPs. ZnO NPs were toxic to this microalga with EC50 of 153/72 mg/L. The toxicity of 200 mg/L ZnO NPs was 59.36% for the cell number, 61.27% for MTT test, and 57.34% for the chlorophyll content. Increase the content of malondialdehyde and hydrogen peroxide in response to increasing the concentration of ZnO NPs was indicated the induction of oxidative stress in N. oculata. The activity of catalase and lactate dehydrogenase increased in the treated cells, while the activity of ascorbate peroxidase was decreased. Concurrently, an increase in the content of carotenoids and phenolic compounds was observed in the treated cells. SEM and TEM analyses confirmed the aggregation of algal cells, damages in cell membrane and atypical changes in morphology of cell wall after NPs treatments. The FTIR results cofirmed the interaction of ZnO NPs with C-H, C-O and C=O groups on the cell surface. All of these changes were indicated the significant toxic impacts of ZnO NPs on the N. oculata cells. Comparison between the results obtained in previous studies with our results showed that the defensive mechanisms of N. oculata probably was not effective against the oxidative stress by >10 mg/L of ZnO NPs, > 5 mg/L of CuO NPs and > 1 mg/L of Ag NPs. Therefore, N. oculata is sensitive to such concentrations of these NPs.

Bioethanol production from defatted biomass of Nannochloropsis oculata microalgae grown under mixotrophic conditions

Microalgal biomass is one of the most promising third-generation feedstocks for bioethanol production because it contains significantly reduced sugar amounts which, by separate hydrolysis and fermentation, can be used as a source for ethanol production. In this study, the defatted microalgal biomass of Nannochloropsis oculata (NNO-1 UTEX Culture LB 2164) was subjected to bioethanol production through acid digestion and enzymatic treatment before being fermented by Saccharomyces cerevisiae (NRRLY-2034). For acid hydrolysis (AH), the highest carbohydrate yield 252.84 mg/g DW was obtained with 5.0% (v/v) H2SO4 at 121°C for 15 min for defatted biomass cultivated mixotrophically on SBAE with respect to 207.41 mg/g DW for defatted biomass cultivated autotrophically (control treatment), Whereas, the highest levels of reducing sugars was obtained With 4.0%(v/v) H2SO4 157.47 ± 1.60 mg/g DW for defatted biomass cultivated mixotrophically in compared with 135.30 mg/g DW for the defatted control treatment. The combination of acid hydrolysis 2.0% (v/v) H2SO4 followed by enzymatic treatment (AEH) increased the carbohydrate yields to 268.53 mg/g DW for defatted biomass cultivated mixotrophically on SBAE with respect to 177.73 mg/g DW for the defatted control treatment. However, the highest levels of reducing sugars were obtained with 3.0% (v/v) H2SO4 followed by enzyme treatment gave 232.39 ± 1.77 for defatted biomass cultivated mixotrophically on SBAE and 150.75 mg/g DW for the defatted control treatment. The sugar composition of the polysaccharides showed that glucose was the principal polysaccharide sugar (60.7%-62.49%) of N. oculata defatted biomass. Fermentation of the hydrolysates by Saccharomyces cerevisiae for the acid pretreated defatted biomass samples gave ethanol yield of 0.86 g/l (0.062 g/g sugar consumed) for control and 1.17 g/l (0.069 g/g sugar consumed) for SBAE mixotrophic. Whereas, the maximum ethanol yield of 6.17 ± 0.47 g/l (0.26 ± 0.11 g/g sugar consumed) was obtained with samples from defatted biomass grown mixotrophically (SBAE mixotrophic) pretreated with acid coupled enzyme hydrolysis.

INFLUÊNCIA DA AGITAÇÃO EM FOTOBIORREATORES PARA O CULTIVO DE MICROALGAS VISANDO A OBTENÇÃO DE COMPOSTOS BIOQUÍMICOS

Introdução: Para o desenvolvimento de um fotobiorreator eficiente a penetração, transporte, distribuição e utilização de luz pelos microrganismos fotossintéticos dentro do sistema são fatores predominantes. Além disso, esses sistemas devem permitir o controle das condições ideias para o desenvolvimento do cultivo, como uma boa homogeneização. Esse parâmetro permite uma exposição de luz igualitária para as células, além de otimizar o ciclo claro/escuro dentro do recipiente, influenciando diretamente nas reações fotossintéticas. A eficiência do mesmo também traz como benefícios uma alta disponibilidade de CO2 levando assim a um melhor controle do pH. Dependendo da escala e do fotobiorreator definido para o cultivo, a mistura pode ser realizada por aeração, agitação mecânica e entre outros. Objetivos: Realizar uma revisão bibliográfica com o intuído de avaliar a influência da agitação na obtenção de compostos com autovalor agregado. Material e Métodos: Realizou-se um levantamento bibliográfico das principais variáveis através das bases cientificas de pesquisa, como Scopus, ScienceDirect e Google acadêmico. Resultados: Uma agitação eficiente em um fotobiorreator é conhecida por trazer grandes produtividades para o sistema, desempenhando deste modo um papel importante na distribuição de luz e nutrientes para as células. Segundo um estudo desenvolvido para avaliar o potencial de algumas microalgas em acumular compostos bioquímicos sob o efeito de diferentes condições de agitação mecânica, os autores obtiveram uma concentração máxima de biomassa de 2.423 mg/L sob velocidade de agitação de 1400 rpm para a espécie Dunaliella salina. Além disso, obtiveram um teor máximo de lipídeos totais, correspondendo a 23%, para a espécie Nannochloropsis oculata sob uma velocidade de agitação de 200 rpm. Conclusão: Portanto, a mistura desempenha um papel significativo no cultivo sendo um mecanismo eficaz para promover turbulência e aumentar a produtividade de um sistema.