Profiling multi-enzyme activities of Aspergillus niger strains growing on various agro-industrial residues

Cryptococcus laurentii: a wild yeast for xylanase production from agricultural by-products

The development of technologies that allow the production of enzymes at a competitive cost is of great importance for several biotechnological applications, and the use of agro-industrial by-products is an excellent alternative to minimize costs and reduce environmental impacts. This study aimed to produce endo-xylanases using agro-industrial substrates rich in hemicellulose as sources of xylan in culture media. For this purpose, the yeast Cryptococcus laurentti and five lignocellulosic materials (defatted rice bran, rice husk, corn cob, oat husks, and soybean tegument), with and without pretreatment, were used as a source of xylan for enzyme production. To insert the by-products in the culture medium, they were dried and treated (if applicable) with 4% (w.v-1) NaOH and then added in a concentration of 2% (w.v-1). The cultures were agitated for 96 h, and the aliquots were removed to determine the enzymatic activities. Among the by-products studied, the maximum activity (8.7 U. mL-1 at pH 7.3) was obtained where rice bran was used. In contrast, corn cob was the by-product that resulted in lower enzyme production (1.6 U.mL-1). Thus, the defatted rice bran deserves special attention in front of the other by-products used since it provides the necessary substrate for producing endo-xylanases by yeast.

Characteristics and kinetics of thermophilic actinomycetes' amylase production on agro-wastes and its application for ethanol fermentation

Thermophilic actinomycetes are commonly found in extreme environments and can thrive and adapt to extreme conditions. These organisms exhibit substantial variation and garnered significant interest due to their remarkable enzymatic activities. This study evaluated the potential of Streptomyces griseorubens NBR14 and Nocardiopsis synnemataformans NBRM9 strains to produce thermo-stable amylase via submerged fermentation using wheat and bean straw. The Box-Behnken design was utilized to determine the optimum parameters for amylase biosynthesis. Subsequently, amylase underwent partial purification and characterization. Furthermore, the obtained hydrolysate was applied for ethanol fermentation using Saccharomyces cerevisiae. The optimal parameters for obtaining the highest amylase activity by NBR14 (7.72 U/mL) and NBRM9 (26.54 U/mL) strains were found to be 40 and 30 °C, pH values of 7, incubation time of 7 days, and substrate concentration (3 and 2 g/100 mL), respectively. The NBR14 and NBRM9 amylase were partially purified, resulting in specific activities of 251.15 and 144.84 U/mg, as well as purification factors of 3.91 and 2.69-fold, respectively. After partial purification, the amylase extracted from NBR14 and NBRM9 showed the highest activity level at pH values of 9 and 7 and temperatures of 50 and 60 °C, respectively. The findings also indicated that the maximum velocity (Vmax) for NBR14 and NBRM9 amylase were 57.80 and 59.88 U/mL, respectively, with Km constants of 1.39 and 1.479 mM. After 48 h, bioethanol was produced at concentrations of 5.95 mg/mL and 9.29 mg/mL from hydrolyzed wheat and bean straw, respectively, through fermentation with S. cerevisiae. Thermophilic actinomycetes and their α-amylase yield demonstrated promising potential for sustainable bio-ethanol production from agro-byproducts.

Fractionation of cassava pectins and their detailed structural analyses using various pectinolytic enzymes

In this study, we analyzed the pectin structure within the pulp of cassava. Cassava pectin, derived from cassava pulp treatment at 120 °C for 90 min, was separated into four fractions (CP-P, CP-SD1, CP-SD2F, and CP-SD2R) based on variations in water solubility, electrical properties, and molecular weights. Sugar composition analysis demonstrated an abundance of homogalacturonan (HG) in CP-P and CP-SD2F, rhamnogalacturonan I (RG-I) in CP-SD2R, and neutral sugars in CP-SD1. Because RG-I possesses a complex structure, we analyzed CP-SD2R using various pectinolytic enzymes. Galactose was the major sugar in CP-SD2R accounting for 49 %, of which 65 % originated from arabinogalactan I, 9 % from galactose and galactooligosaccharides, 5 % from arabinogalactan II, and 11 % from galactoarabinan. Seventy-four percent of arabinose in CP-SD2R was present as galactoarabinan. The methylation (DM) and acetylation (DAc) degrees of cassava pectin were 11 and 15 %, respectively. The HG and RG-I regions exhibited DAc values of 5 and 44 %, respectively, signifying the high DAc of RG-I compared to HG. Information derived from the structural analysis of cassava pectin will enable efficient degradation of pectin and cellulose, leading to the use of cassava pulp as a raw material for biorefineries.

High-level production of Aspergillus niger prolyl endopeptidase from agricultural residue and its application in beer brewing

BACKGROUND

Prolyl endopeptidase from Aspergillus niger (AN-PEP) is a prominent serine proteinase with various potential applications in the food and pharmaceutical industries. However, the availability of efficient and low-cost AN-PEP remains a challenge owing to its low yield and high fermentation cost.

RESULTS

Here, AN-PEP was recombinantly expressed in Trichoderma reesei (rAN-PEP) under the control of the cbh1 promoter and its secretion signal. After 4 days of shaking flask cultivation with the model cellulose Avicel PH101 as the sole carbon source, the extracellular prolyl endopeptidase activity reached up to 16.148 U/mL, which is the highest titer reported to date and the secretion of the enzyme is faster in T. reesei than in other eukaryotic expression systems including A. niger and Komagataella phaffii. Most importantly, when cultivated on the low-cost agricultural residue corn cob, the recombinant strain was found to secret a remarkable amount of rAN-PEP (37.125 U/mL) that is twice the activity under the pure cellulose condition. Furthermore, treatment with rAN-PEP during beer brewing lowered the content of gluten below the ELISA kit detection limit (< 10 mg/kg) and thereby, reduced turbidity, which would be beneficial for improving the non-biological stability of beer.

CONCLUSION

Our research provides a promising approach for industrial production of AN-PEP and other enzymes (proteins) from renewable lignocellulosic biomass, which provides a new idea with relevant researchers for the utilization of agricultural residues.

A comparative study of Cellulomonas sp. and Bacillus sp. in utilizing lignocellulosic biomass as feedstocks for enzyme production

The demand for enzymes is increasing continuously due to their applications in various avenues. The pectin-hydrolyzing bacteria, Cellulomonas sp. and Bacillus sp., isolated from forest soil have the potential to produce industrially important enzymes (pectinase, PGase, Cellulase, and xylanase). However, these bacteria have different optimal cultural conditions for pectinase production. The optimal cultural conditions for Cellulomonas sp. were room temperature (25-26℃), pH 7, 1% inoculum volume, and 1.5% citrus pectin with 8.82 ± 0.92 U/mL pectinase activity. And Bacillus sp. illustrated the highest pectinase activity (12.35 ± 0.72 U/mL) at room temperature, pH 10, 1% inoculum volume, and 1.5% pectin concentration. Among the different agro-wastes, the orange peel was found to be the best substrate for pectinase, PGase, and cellulase activity whereas barley straw for xylanase activity. Further, Cellulomonas sp. and Bacillus sp. illustrated higher pectinase activity from commercial pectin compared to orange peel showing their preference for commercial citrus pectin. In addition, the optimization by the Box-Behnken design increased pectinase activity for Cellulomonas sp., while a noticeable increase in activity was not observed in Bacillus sp. Besides, all the agro-wastes exploited in this study can be used for pectinase, PGase, and xylanase production but not cellulase. The study revealed that each bacteria has its specific optimal conditions and there is a variation in the capacity of utilizing the various lignocellulosic biomass.

Biomass-Degrading Enzyme(s) Production and Biomass Degradation by a Novel Streptomyces thermocarboxydus

Modern society has a great challenge to decrease waste and minimize the adverse effects of wastes on the economy, environment, and individual health. Thus, this study focuses on the use of eight agro-wastes (banana peel, barley straw, canola straw, pomegranate peel, orange peel, pumpkin pulp+seeds, maple leaf, and brewer's spent grains) by a novel bacterium (Streptomyces thermocarboxydus) for enzymes production. Further, the study explored the subsequent degradation of those wastes by the bacterium. This bacterium was isolated from forest soil and identified as Streptomyces thermocarboxydus by 16S rRNA sequence analysis. The biodegrading capability of S. thermocarboxydus was determined by observing the clear zone around the colony cultured on the agar plate containing the different biomasses as sole carbon sources and calculating the substrate degradation ratios. Furthermore, scanning electron microscopy images of eight agro-wastes before and after bacterial treatment and weight loss of agro-wastes revealed the bacterium degraded the biomasses. The different trends of enzyme activities were observed for various wastes, and the maximum activity depended on the type of agro-wastes. Overall, S. thermocarboxydus was found to be a potential candidate for pectinase and xylanase production. The enzyme production varies with the concentration of the biomasses.

Development of sequence-characterized amplified region (SCAR) markers for accurate and differential identification of multienzyme-producing and non-enzymatic Aspergillus strains of industrial importance

Aspergillus strains are known to produce multiple enzymes of industrial importance. To screen Aspergillus isolates and select a strain with the ability to produce multiple enzymes and discriminate it from non-enzymatic strains, a rapid and accurate approach is required. With this background, a DNA fingerprinting-based study was conducted to develop a simple but accurate molecular detection method with the potential to discriminate multienzyme-producing Aspergillus strains from non-enzymatic strains, irrespective of species. To achieve this, Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR was employed to derive group-specific Sequence Characterized Amplified Region (SCAR) markers (i.e., markers corresponding to PCR amplicons of known DNA sequence). To this end, both group-specific (multienzyme-producing and non-enzymatic Aspergillus group) SCAR markers were sought by comparing the ERIC fingerprint profiles and used to develop primers for use in specific and differential identification of multienzyme-producing Aspergillus isolates. As an outcome, the two SCAR-PCR formats were developed. One format is for specific identification of multienzyme-producing Aspergillus strains (SCAR-PCR1), and the other for identifying non-enzymatic Aspergillus strains (SCAR-PCR2). Both SCAR-PCRs were able to discriminate between these two contrasting groups. These formats are simple but accurate and rapid compared to the time-consuming and laborious conventional methods. Therefore, they could be efficient as an alternative strategy for the high-throughput screening of industrially important Aspergillus strains.

Optimization of multiple enzymes production by fermentation using lipid-producing Bacillus sp

The present study identified the pectinase-producing bacterium isolated from the contaminated broth as Bacillus sp. on 16S rDNA sequence analysis. The bacterium illustrated water-like droplets on the colony grown on the Sabouraud dextrose agar plate. It also exhibited multi-enzymes activities, such as pectinase, polygalacturonase, xylanase, and cellulase by using various agro-wastes as low-cost substrates. The orange peel was observed to be the best substrate among the agro-wastes used for maximum multi-enzymes (pectinase, polygalacturonase, xylanase, and cellulase). However, the bacterium demonstrated its capability to produce different enzymes according to the different substrates/agro-wastes used. The Plackett-Burman design was used to determine the essential influencing factors, while the Box Behnken design response surface methodology was for optimizing cultural conditions. At their optimal conditions (40°C incubation temperature, 24 h of incubation period, 1% w/v orange peel, and 2% v/v inoculum volume), the bacterium exhibited the maximum pectinase (9.49 ± 1.25 U/ml) and xylanase (16.27 ± 0.52 U/ml) activities. Furthermore, the study explored the ability of the bacterium to produce bacterial lipids and observed about 25% bacterial lipid content on a dry weight basis. Therefore, the bacterium is a good candidate for producing important multi-enzymes and subsequent agro-waste degradation controlling the environment, and facilitating waste management. Also, the bacterium can be a potential feedstock in producing renewable biofuel.