Effect of Several Pretreatments on the Lactic Acid Production from Exhausted Sugar Beet Pulp

Production of lactic acid from pasta wastes using a biorefinery approach

A total of 398 kt of pasta waste (PW), generated during the production process of pasta, were produced in 2021. Due to its chemical composition and practically zero cost, PW has already been studied as a raw material for the production of lactic acid (LA) through fermentations. The main objective of this article was to improve the economic viability of the process by replacing commercial enzymes, necessary for starch hydrolysis in PW, with raw enzymes also produced from wastes. Enzyme synthesis was achieved through solid-state fermentation (SsF) of wheat bran by Aspergillus awamori or Aspergillus oryzae at various moisture contents. The maximum amylase activity (52 U/g dry solid) was achieved after 2 days of fermentation with A. awamori at 60% of moisture content. After that, the enzymes were used to hydrolyse PW, reaching 76 g/L of total sugars, 65 g/L of glucose and a yield of 0.72 g_glu/g_ds with the enzymes produced by A. awamori. Subsequently, the hydrolysate was fermented into LA using Bacillus coagulans A559, yielding 52 g/L and 49 g/L with and without yeast extract, respectively. Remarkably, compared to the process with commercial enzymes, a higher LA yield was reached when enzymes produced by SsF were added (0.80 g_LA/g_glu). Furthermore, the productivities between the two processes were similar (around 3.9 g/L/h) which highlights that yeast extract is not necessary when using enzymes produced by SsF.

Fermentative Lactic Acid Production From Lignocellulosic Feedstocks: From Source to Purified Product

The second (lignocellulosic biomass and industrial wastes) and third (algal biomass) generation feedstocks gained substantial interest as a source of various value-added chemicals, produced by fermentation. Lactic acid is a valuable platform chemical with both traditional and newer applications in many industries. The successful fractionation, separation, and hydrolysis of lignocellulosic biomass result in sugars' rich raw material for lactic acid fermentation. This review paper aims to summarize the investigations and progress in the last 5 years in lactic acid production from inexpensive and renewable resources. Different aspects are discussed-the type of raw materials, pretreatment and detoxification methods, lactic acid-producers (bacteria, fungi, and yeasts), use of genetically manipulated microorganisms, separation techniques, different approaches of process organization, as well as main challenges, and possible solutions for process optimization.

Valorization of sugar beet pulp to value-added products: A review

The processing of sugar beet in the sugar production industry releases huge amounts of sugar beet pulp as waste which can be considered a valuable by-product as a source of cellulose, hemicellulose, and pectin. Valorization of sugar beet pulp into value added products occurs through acid hydrolysis, hydrothermal techniques, and enzymatic hydrolysis. Biochemical conversion of beet pulp into simple fermentable sugars for producing value added products occurs through enzymatic hydrolysis is a cost effective and eco-friendly process. While beet pulp has predominantly been used as a fodder for livestock, recent developments in its biotechnological valorization have unlocked its value as a feedstock in the production of biofuels, biohydrogen, biodegradable plastics, and platform chemicals such as lactic acid, citric acid, alcohols, microbial enzymes, single cell proteins, and pectic oligosaccharides. This review brings forward recent biotechnological developments made in the valorization of sugar beet pulp into valuable products.