Effects of Poly(Galacturonic Acid)on the Properties and Structure of Konjac Glucomannan Aerogel

A novel konjac glucomannan(KGM)/poly(galacturonic acid)(PGuA)mixed aerogel(KGM/PGuA)was prepared via a vacuum freeze-drying method,and its interaction mechanism was studied.The rheology results showed that KGM/PGuA mixed gels are typical non-Newtonian pseudoplastic fluids,and PGuA increased the viscosity of the composite aerogel and strengthened the molecular entanglement between KGM and PGuA molecules.The structures of KGM/PGuA aerogels were characterized by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results show that the intermolecular interactions were mainly hydrogen bonding.Dense and uniform porous structures were found in the aerogel microstructures.All these findings indicate that PGuA has the effect of enhancing the KGM gel structure,and KGM/PGuA gels with porous structures might be potential materials for use in food and biomedical areas for loading active materials.

Effect of pyrite, elemental sulfur and ferrous ions on EPS production by metal sulfide bioleaching microbes

Extracellular polymeric substances （EPS） produced by acidophilic bioleaching microorganisms play an important role in the production of acid mine drainage and metal sulfide bioleaching. EPS mediate the contact between microbial cells and growth substrates, having a pivotal role in organic film formation and bacterium-substratum interactions. The production and chemical composition of EPS produced by seven bioleaching strains grown with different substrates were studied. Analysis of the EPS extracted from these strains indicated that the EPS consisted of carbohydrates, proteins and galacturonic acid. The contents of EPS, carbohydrates, proteins and galacturonic acid of EPS were largely related to the kind of strain used and culture condition. The results show that EPS productions of microbes grown with pyrite were significantly higher than those of microbes grown with sulfur or FeSO4·7H2O. The highest EPS production of the seven acidiphilic strains was （159.43±3.93） mg/g, which was produced by Leptospirillum ferriphilum CBCBSUCSU208015 when cultivated with pyrite.

Evaluation of sources and methods of pectin extraction from fruit and Vegetable wastes:A Systematic Literature Review(SLR)

The potentially commercial sources of pectin are limited.Researchers have studied different extraction methods using a wide variety of fruits and vegetables to obtain pectins with better characteristics.The objective of this work was to identify the methods used in the extraction of pectin,the most used sources and the operation parameters that enable the achievement of higher yields and the final characteristics of the obtained product.These are based on bibliometric methods for exploring the structure of knowledge in this field for the last twelve years.To this end,a Systematic Literature Review(SLR)using the SCOPUS database was carried out,which allowed identifying keywords and formulating search equations to find scientific articles on the topic in question.After selecting the articles,a detailed reading of these works was carried out,and the used extraction methods and the evaluated variables,yields and characteristics were analyzed.This article compares and discusses the effects of conventional and non-conventional pectin extraction techniques,which may provide valuable information on sources and alternatives for pectin extraction to ease decision-making in future research.The acid hydrolysis method remains the most widely used pectin extraction technique since it provides higher yields.It is followed by microwave-assisted extraction,ultrasonic extraction,and the enzymatic method,which have a greater capacity to deliver pectins with high methoxyl content.Finally,non-conventional methods such as radiofrequency,ohmic heating,and aqueous two-phase extraction are presented as promising techniques that offer pectins with a high degree of esterification in addition to good yields.