Isolation of Saccharomyces Cerevisiae from Pineapple and Orange and Study of Metal's Effectiveness on Ethanol Production

Production of bioethanol from sweet sorghum [Sorghum bicolor L.] juice using yeast isolated from fermented sweet sorghum juice

As a sugar-rich plant with no impact on global warming and food security, sweet sorghum can be exploited as an alternative source of renewable bioenergy. This study aimed to examine the potential of sweet sorghum juice for the generation of bioethanol using yeast isolated from the juice. The °Brix of sweet sorghum juice was measured using a digital refractometer. Additionally, 18 wild yeasts isolated from fermented sweet sorghum juice were subjected to various biochemical tests to describe them to identify potential yeast for ethanol production. The morphological and biochemical analyses of the yeasts revealed that all of the yeast isolates were most likely members of the genus Saccharomyces. The most ethanol-tolerant yeast isolate SJU14 was employed for sweet sorghum juice fermentation. A completely randomized factorial design was used with various fermentation parameters, primarily pH, temperature, and incubation period. Then ethanol content was determined using a potassium dichromate solution. According to the ANOVA, the highest ethanol content (18.765%) was produced at 30/26 °C, pH 4.5, and incubated for 96 h. Sweet sorghum juice was found to be an excellent source of potent yeasts, which have important industrial properties like the capacity to grow at high ethanol and glucose concentrations. Moreover, it can be utilized as a substitute substrate for the manufacturing of bioethanol production to lessen the environmental threat posed by fossil fuels. Further research is, therefore, recommended to develop strategically valuable applications of sweet sorghum for enhancing the food system and mitigating climate change.

A Novel Halo-Acid-Alkali-Tolerant and Surfactant Stable Amylase Secreted from Halophile Bacillus siamensis F2 and Its Application in Waste Valorization by Bioethanol Production and Food Industry

The extracellular amylase production level by the moderate halophile Bacillus siamensis F2 was optimized, and the enzyme was biochemically characterized. The culture parameters for NaCl, carbon, nitrogen, pH, and temperature were optimized for high titers of amylase production. Growing B. siamensis F2 cultures in Great Salt Lake-2 medium with additions of (in g/L) NaCl (100), starch (30), yeast extract (2), KNO3 (2), and MgSO4 (1) at pH 8, 30 °C resulted in the maximum amylase production (4.2 U/ml). The amylase was active across a wide range of salinities (0 to 30% NaCl), pH (5.0-10.0), and temperatures (20-70 °C) and showed good stability with surfactants (sodium dodecyl sulfate (SDS) and Triton X-100); hence, it was identified as halo-acid-alkali-tolerant and surfactant stable. Temperature, pH, and salinity were optimal for amylase activity at 50 °C, pH 7, and 5% NaCl, respectively. It also generates amylase by utilizing agricultural wastes like sugarcane bagasse, sweet potato peel, and rice husk. Based on the performance of B. siamensis F2 using agricultural wastes and synthesizing amylase, the current study attempted to produce bioethanol by coculturing with baker's yeast using sugarcane bagasse and sweet potato peel as a substrate, which yielded 47 and 57 g/L of bioethanol, respectively. Besides bioethanol production, amylase secreted by F2 was also employed for juice clarification for better yield and clarity and for softening dough to produce better-quality buns. This novel amylase may have many potential applications in waste valorization, biorefinery sectors, and food industries.

Non-conventional yeast strains: Unexploited resources for effective commercialization of second generation bioethanol

The conventional yeast (Saccharomyces cerevisiae) is the most studied yeast and has been used in many important industrial productions, especially in bioethanol production from first generation feedstock (sugar and starchy biomass). However, for reduced cost and to avoid competition with food, second generation bioethanol, which is produced from lignocellulosic feedstock, is now being investigated. Production of second generation bioethanol involves pre-treatment and hydrolysis of lignocellulosic biomass to sugar monomers containing, amongst others, d-glucose and D-xylose. Intrinsically, S. cerevisiae strains lack the ability to ferment pentose sugars and genetic engineering of S. cerevisiae to inculcate the ability to ferment pentose sugars is ongoing to develop recombinant strains with the required stability and robustness for commercial second generation bioethanol production. Furthermore, pre-treatment of these lignocellulosic wastes leads to the release of inhibitory compounds which adversely affect the growth and fermentation by S. cerevisae. S. cerevisiae also lacks the ability to grow at high temperatures which favour Simultaneous Saccharification and Fermentation of substrates to bioethanol. There is, therefore, a need for robust yeast species which can co-ferment hexose and pentose sugars and can tolerate high temperatures and the inhibitory substances produced during pre-treatment and hydrolysis of lignocellulosic materials. Non-conventional yeast strains are potential solutions to these problems due to their abilities to ferment both hexose and pentose sugars, and tolerate high temperature and stress conditions encountered during ethanol production from lignocellulosic hydrolysate. This review highlights the limitations of the conventional yeast species and the potentials of non-conventional yeast strains in commercialization of second generation bioethanol.

Identification of microorganisms from fermented biowaste and the potential for wastewater treatment

Food loss or waste is a far-reaching problem and has indeed become a worrying issue that is growing at an alarming rate. Fruits and vegetables are lost or wasted at the highest rate among the composition of food waste. Furthermore, the world is progressing toward sustainable development; hence, an efficient approach to valorise fruit and vegetable waste (FVW) is necessary. A simple phenotypic characterisation of microbiota isolated from the fermented FVW was conducted, and its effectiveness toward wastewater treatment was investigated. Presumptive identification suggested that yeast is dominant in this study, accounting for 85% of total isolates. At the genus level, the enriched medium's microbial community consists of Saccharomyces, Bacillus and Candida. Ammonium in the wastewater can enhance certain bacteria to grow, such as lactic acid bacteria, resulting in decreased NH₄⁺ concentration at the end of the treatment to 0.5 mg/L. In addition, the fermented biowaste could reduce PO₄^3- by 90% after the duration of treatment. Overall, FVW is a valuable microbial resource, and the microbial population enables a reduction in organic matter such as NH₄⁺ and PO₄^3-. This study helps explore the function and improve the effectiveness of utilising biowaste by understanding the microorganisms responsible for producing eco-enzyme.

Isolation and characterization of bioethanol producing wild yeasts from bio-wastes and co-products of sugar factories

Purpose

Yeasts are widely used for the production of bioethanol from biomasses rich in sugar. The present study was aimed at isolating, screening, and characterizing fermentative wild yeast recovered from bio-waste and co-products of Ethiopian sugar factories for bioethanol production using sugarcane molasses as a substrate.

Method

The wild yeasts were identified according to their cellular morphology and D1/D2 and ITS1-5.8S-ITS2 rDNA sequencing. Analysis of ethanol and by-product concentration was done by HPLC equipped with a UV detector. Higher alcohols, acetaldehyde, and methanol were analyzed using GC-MS equipped with a flame ionization detector (FID).

Result

Seven strains (Meyerozyma caribbica MJTm3, Meyerozyma caribbica MJTPm4, Meyerozyma caribbica SHJF, Saccharomyces cerevisiae TA2, Wickerhamomyces anomalus MJTPm2, Wickerhamomyces anomalus 4m10, and Wickerhamomyces anomalus HCJ2F) were found tolerant to 18% (v/v) ethanol, whereas one strain Meyerozyma caribbica MJTm3 tolerated 20%. These strains also showed tolerance to 45°C, 50% of sugar, and pH 2–10. Meyerozyma caribbica MJTm3 produced 12.7% (v/v) of alcohol with an actual ethanol concentration of 26 g L−1, an ethanol yield of 47%, 78% of theoretical yield, and a productivity of 0.54 g L−1 h−1 from 30 °Brix of molasses at 48 h incubation under laboratory scale. Based on the one variable at a time optimization (OVAT), the optimal parameters for maximum bioethanol production were at initial pH 5.5, 35 °Brix, 30°C, 15% inoculum size, 150 rpm, 4 g L−1 di-ammonium phosphate supplement, and 48 h incubation. Under these optimum conditions, 14% (v/v) alcohol, 42 g L−1 actual ethanol concentration, 69% ethanol yield, 89% of theoretical yield, and productivity of 0.88 g L−1 h−1 were obtained.

Conclusion

These results indicated that M. caribbica MJTm3 should further be evaluated, optimized, and improved for industrial bioethanol production due to its fermentation potential.

Current Ethanol Production Requirements for the Yeast Saccharomyces cerevisiae

An increase in global energy demand has caused oil prices to reach record levels in recent times. High oil prices together with concerns over CO₂ emissions have resulted in renewed interest in renewable energy. Nowadays, ethanol is the principal renewable biofuel. However, the industrial need for increased productivity, wider substrate range utilization, and the production of novel compounds leads to renewed interest in further extending the use of current industrial strains by exploiting the immense, and still unknown, potential of natural yeast strains. This review seeks to answer the following questions: (a) which characteristics should S. cerevisiae have for the current production of first- and second-generation ethanol? (b) Why are alcohol-tolerance and thermo-tolerance characteristics required? (c) Which genes are related to these characteristics? (d) What are the advances that can be achieved with the isolation of new organisms from the environment?

Different plant compartments, different yeasts: the example of the bromeliad phyllosphere

The plant phyllosphere is one of the largest sources of microorganisms, including yeasts. In bromeliads, the knowledge of yeasts is dispersed and still incipient. To understand the extent of our knowledge on the subject, this review proposes to compile and synthesize existing knowledge, elucidating possible patterns, biotechnological and taxonomic potentials, bringing to light new knowledge, and identifying information gaps. For such, we systematically review scientific production on yeasts in bromeliads using various databases. The results indicated that the plant compartments flowers, fruits, leaves, and water tank (phytotelma) have been studied when focusing on the yeast community in the bromeliad phyllosphere. More than 180 species of yeasts and yeast-like fungi were recorded from the phyllosphere, 70% were exclusively found in one of these four compartments and only 2% were shared among all. In addition, most of the community had a low frequency of occurrence, and approximately half of the species had a single record. Variables such as bromeliad subfamilies and functional types, as well as plant compartments, were statistically significant, though inconclusive and with low explanatory power. At least 50 yeast species with some biotechnological potentials have been isolated from bromeliads. More than 90% of these species were able to produce extracellular enzymes. In addition, other biotechnological applications have also been recorded. Moreover, new species have been described, though yeasts were only exploited in approximately 1% of the existing bromeliads species, which highlights that there is still much to be explored. Nevertheless, it appears that we are still far from recovering the completeness of the diversity of yeasts in this host. Furthermore, bromeliads proved to be a good ecological model for prospecting new yeasts and for studies on the interaction between plants and yeasts. In addition, the yeast community diverged among plant compartments, establishing bromeliads as a microbiologically complex and heterogeneous mosaic. This article is protected by copyright. All rights reserved.

Optimization, Purification and Antitumor Activity of Kodamaea ohmeri ANOMY L-Asparaginase Isolated from Banana Peel

OBJECTIVE

L-Asparaginase is an important enzyme that converts L-asparagine to L-aspartate and ammonia. Microbial L-asparaginase has important applications as anticancer and food processing agents.

METHODS

This study reported the isolation, screening of a local yeast isolate from banana peel for L-asparaginase production using submerged fermentation, optimization of the production, purification, and anticancer assay of L-asparaginase. The yeast isolate was identified as Kodamaea ohmeri ANOMY based on the analysis of nuclear large subunit (26S) rDNA partial sequences. It was a promising L-asparaginase producer with a specific activity of 3059±193 U/mg in a non-optimized medium. The classical one-variable-at-a-time method was used to optimize the production medium components, and it was found that the elimination of K2HPO4 from the medium increased L-asparaginase specific activity (3100.90±180 U/mg).

RESULTS

Statistical optimization of L-asparaginase production was done using Plackett-Burman and Box-Behnken designs. The production medium for the maximum L-asparaginase specific activity (8500±578U/mg) was as follows (g/L): L-asparagine (7.50), NaNO3 (0.50), MgSO₄.7H₂O (0.80), KCl (0.80) associated with an incubation period of 5 days, inoculum size of 5.60 %, and pH (7.0). The optimization process increased L-asparaginase production by 2.78-fold compared to the non-optimized medium. L-Asparaginase was purified using ammonium sulphate precipitation followed by gel filtration on a Sephadex G-100 column. Its molecular weight was 66 KDa by SDS-PAGE analysis.

CONCLUSION

The cell morphology technique was used to evaluate the anticancer activity of L-asparaginase against three different cell lines. L-Asparaginase inhibited the growth of HepG-2, MCF-7, and HCT-116 cells at a concentration of 20, 50, and 60 μL, respectively.

d-Xylose consumption by nonrecombinant Saccharomyces cerevisiae: A review

Xylose is the second most abundant sugar in nature. Its efficient fermentation has been considered as a critical factor for a feasible conversion of renewable biomass resources into biofuels and other chemicals. The yeast Saccharomyces cerevisiae is of exceptional industrial importance due to its excellent capability to ferment sugars. However, although S. cerevisiae is able to ferment xylulose, it is considered unable to metabolize xylose, and thus, a lot of research has been directed to engineer this yeast with heterologous genes to allow xylose consumption and fermentation. The analysis of the natural genetic diversity of this yeast has also revealed some nonrecombinant S. cerevisiae strains that consume or even grow (modestly) on xylose. The genome of this yeast has all the genes required for xylose transport and metabolism through the xylose reductase, xylitol dehydrogenase, and xylulokinase pathway, but there seems to be problems in their kinetic properties and/or required expression. Self-cloning industrial S. cerevisiae strains overexpressing some of the endogenous genes have shown interesting results, and new strategies and approaches designed to improve these S. cerevisiae strains for ethanol production from xylose will also be presented in this review.

Evaluation of divergent yeast genera for fermentation-associated stresses and identification of a robust sugarcane distillery waste isolate Saccharomyces cerevisiae NGY10 for lignocellulosic ethanol production in SHF and SSF

BACKGROUND

Lignocellulosic hydrolysates contain a mixture of hexose (C6)/pentose (C5) sugars and pretreatment-generated inhibitors (furans, weak acids and phenolics). Therefore, robust yeast isolates with characteristics of C6/C5 fermentation and tolerance to pretreatment-derived inhibitors are pre-requisite for efficient lignocellulosic material based biorefineries. Moreover, use of thermotolerant yeast isolates will further reduce cooling cost, contamination during fermentation, and required for developing simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SScF), and consolidated bio-processing (CBP) strategies.

RESULTS

In this study, we evaluated thirty-five yeast isolates (belonging to six genera including Saccharomyces, Kluyveromyces, Candida, Scheffersomyces, Ogatea and Wickerhamomyces) for pretreatment-generated inhibitors {furfural, 5-hydroxymethyl furfural (5-HMF) and acetic acid} and thermotolerant phenotypes along with the fermentation performances at 40 °C. Among them, a sugarcane distillery waste isolate, Saccharomyces cerevisiae NGY10 produced maximum 49.77 ± 0.34 g/l and 46.81 ± 21.98 g/l ethanol with the efficiency of 97.39% and 93.54% at 30 °C and 40 °C, respectively, in 24 h using glucose as a carbon source. Furthermore, isolate NGY10 produced 12.25 ± 0.09 g/l and 7.18 ± 0.14 g/l of ethanol with 92.81% and 91.58% efficiency via SHF, and 30.22 g/l and 25.77 g/l ethanol with 86.43% and 73.29% efficiency via SSF using acid- and alkali-pretreated rice straw as carbon sources, respectively, at 40 °C. In addition, isolate NGY10 also produced 92.31 ± 3.39 g/l (11.7% v/v) and 33.66 ± 1.04 g/l (4.26% v/v) ethanol at 40 °C with the yields of 81.49% and 73.87% in the presence of 30% w/v glucose or 4× concentrated acid-pretreated rice straw hydrolysate, respectively. Moreover, isolate NGY10 displayed furfural- (1.5 g/l), 5-HMF (3.0 g/l), acetic acid- (0.2% v/v) and ethanol-(10.0% v/v) tolerant phenotypes.

CONCLUSION

A sugarcane distillery waste isolate NGY10 demonstrated high potential for ethanol production, C5 metabolic engineering and developing strategies for SSF, SScF and CBP.

Bioethanol production using vegetable peels medium and the effective role of cellulolytic bacterial (Bacillus subtilis) pre-treatment

Background:  The requirement of an alternative clean energy source is increasing with the elevating energy demand of modern age. Bioethanol is considered as an excellent candidate to satiate this demand. Methods: Yeast isolates were used for the production of bioethanol using cellulosic vegetable wastes as substrate. Efficient bioconversion of lignocellulosic biomass into ethanol was achieved by the action of cellulolytic bacteria ( Bacillus subtilis).  After proper isolation, identification and characterization of stress tolerances (thermo-, ethanol-, pH-, osmo- & sugar tolerance), optimization of physiochemical parameters for ethanol production by the yeast isolates was assessed. Very inexpensive and easily available raw materials (vegetable peels) were used as fermentation media. Fermentation was optimized with respect to temperature, reducing sugar concentration and pH. Results: It was observed that temperatures of 30°C and pH 6.0 were optimum for fermentation with a maximum yield of ethanol. The results indicated an overall increase in yields upon the pretreatment of Bacillus subtilis; maximum ethanol percentages for isolate SC1 obtained after 48-hour incubation under pretreated substrate was 14.17% in contrast to untreated media which yielded 6.21% after the same period. Isolate with the highest ethanol production capability was identified as members of the ethanol-producing Saccharomyces species after stress tolerance studies and biochemical characterization using Analytical Profile Index (API) ® 20C AUX and nitrate broth test. Introduction of Bacillus subtilis increased the alcohol production rate from the fermentation of cellulosic materials. Conclusions: The study suggested that the kitchen waste can serve as a raw material in ethanol fermentation.