Optimisation of pre-harvest sago frond sap for the production of l-lactic acid using Lactococcus lactis IO-1

Abstract

The major restriction of sago palm plantation is the long maturation period for the starch extraction. As such, alternative commodity has to be identified to increase commercial value of sago palm especially from the by-product. Sago frond has been harvested to have numerous advantages as an alternative substrate for the production of biomaterial and biofuel such as lactic acid and bioethanol. This study focuses on effective approach to maximise the concentration of sugar in the substrate and to identify the ideal concentration of sago frond sap (SFSp) as sole media to produce l-lactic acid and grow L. lactis IO-1. Result shows that SFSp extracted from sago rachis using a roller press machine contained glucose (43.8 g/L), xylose (17.3 g/L) as free sugars and starch (5.55 g/L). Combination of enzymatic hydrolysis and sterilisation pre-treatment was found to maximise the concentration of total carbon source (68 g/L) and sterilised sago frond sap suitable to be used for fermentation process. The ideal concentration of SFSp that was determined at 50% dilution produces the highest amount of l-lactic acid (24.02 g/L) synergist by most efficient sugar consumption (89.93%). The use of SFSp as fermentation medium for l-lactic acid production generated maximum biomass concentration of 14.53 g/L. The utilisation of SFSp extracted from pre-harvest sago frond as substrate promote efficiency of l-lactic acid production associated to exceptional growth performance of L. lactis IO-1. In conclusion, the concept of utilizing by-product from sago palm as novel raw material promise reliable resources and superiority of L. lactis IO-1 to metabolise sugar in SFSp promote lucrative and ethical production of l-lactic acid.

Introduction

The sago palm industry is one of the major industrial crop that contribute to the Gross Domestic Product (GDP) to Sarawak, mainly for the production of sago starch. Sarawak is one of the biggest sago starch exporter in the world, generating about 200,000 tons and exporting 47, 000 tons annually to support global starch supply. As reported by Ministry of Plantation Industries and Commodities Malaysia (MPIC, 2012), increasing global starch demand, the export value of sago starch increased from RM 135/ton in 1970 to RM 2000/ton in 2010. Sago starch is utilised mainly for food production, such as for the manufacturing of vermicelli, bread, cracker, biscuits and many traditional delicacies. In addition, sago starch is used as raw material to produce high fructose syrup and glucose as an ideal alternative to reduce dependency on imported corn starch. Along with tapioca, sago starch is also used for the manufacturing of monosodium glutamate (MSG). Industrial grade sago starch is used as an extender for urea formaldehyde adhesive in the wood industry, an alternative to hydroxyethyl cellulose to control fluid loss in the petroleum industry, stable and long-lasting biodegradable material for the production of plastic and cheap substrate for fermentation industries such as for the production of biofuel (Bujang, 1999; Muljana et al., 2016).

According to Department of Agriculture (DOA), Department of Agriculture Malaysia (2021), the amount of sago starch production in 2020 was only 134,249 Mt which is reduce about 27% since the last decade. The reduction of sago starch productivity is the result of sago palm deforestation where the sago plantation area was decrease for 45% since 2010 to 2020. Sago starch only accommodates 0.05% of the world starch demand, mainly produced from maize, cassava, potato, and rice. However, sago palm offers higher land use efficiency with 24 MT/ha/year productivity compared to rice (6 MT/ha/year), maize (5.5 MT/ha/year), wheat (5 MT/ha/year) and potato (2.5 MT/ha/year) (Bujang and Ahmad, 1999). Sago palm also possessed incredible ability to adept in extreme condition where most of the cash crop cannot grow such as at highly acidic peat soil allow sago palm to grow well near river banks, lakes and wet soil. Sago palm also can survive from catastrophic natural disaster such as wildfire and prolong flood (Bujang, 2015). These advantages will ease sago farmers to recover from the disaster by reducing time and cost for replanting. Significant with the rapid growth of the world population, the global starch demand projected to increase at the rate of 7.7%, equivalent to 3.85 million tons annually. Malaysia expected to produce 2.4 million tons of sago starch worth 4.8 billion Ringgit Malaysia gross revenue by providing 250, 000 ha of land for sago palm plantation by 2020 to fulfil the global starch demand due to land efficiency and productivity of the sago palm (Department of Agriculture Malaysia, 2021). However, the vision was interrupted by the inhibited expansion of the sago plantation area that eventually decreased from 2010 to 2020. Sago palm plantation area is positively correlated to the productivity of the sago starch; hence, limited sago palm plantation restrains the supply of raw material for the production of sago starch. Not only there is no new sago palm plantation area; the existing area is gradually decreasing because of sago deforestation to be replaced with fast cash crop.

The primary factor that suppresses sago palm plantation development is the long period of the maturation process for the palm to be harvested that usually required 12–15 years for swampy peat soil and 8–12 years if planted on mineral soil. In between the maturation process, there is no available commodity that can be obtained from these plantations, exacerbating the commercial value of the sago industry as a whole (MPIC, 2014). Traditional application of sago frond as material for making roof and handicraft has inspired the researchers to utilise sago frond as raw a material for the production of high-value products as supplementation commodity from sago plantation through the implementation of modern technology while waiting for the sago palm to be harvestable. The harvesting activity of matured sago palm discard a massive amount of sago frond in the farm; meanwhile, the sago frond from growing sago palm is pruned to enhance the growth performance and maximise the productivity of the mother trunk (matured palm) (Nabeya et al., 2013). Hence, those practices result in substantial accumulation of biomass that can be actually utilised as raw material to produce high-value products such as lactic acid and biofuel.

An increase in the usage of food-based crops raises an ethical concern about the usage of food resources to produce chemical and biofuel that may compromise global food security and safety, especially for poor and developing countries. Meanwhile, several studies on lactic acid production indicate that the conventional downstream processing of lactic acid cannot be assured economic. This is because of the large production and recovery costs and sophisticated nature of the biological process, leading to the failures of numerous large-scale lactic acid productions (Tong et al., 2004).

Hence, alternative raw materials such as agricultural by-products to produce lactic acid must be prioritised to ensure a sustainable global food supply. The application of fermentation produces not only high quality and pure lactic acid but also cultivate superior lactic acid bacteria (LAB) that can be developed as a probiotic strain or effective microorganism (EM) later can be used in various applications such as food supplementation to prevent gastrointestinal disease in human or animal. EM is commonly used in the agricultural industry to improve the production of compost fertilizer, stimulate the growth performance of plant by reconditioning the soil and used as an inoculant to improve the quality and enhance the stability of silage for animal feed to support the growth of livestock industry.

Therefore, this research aims to emphasize the potential of sago frond obtained from growing sago palm to establish novel commodity from sago palm plantation. The implementation of an effective method with eligible LAB for producing high purity l-lactic acid using a by-product from sago palm plantation as sole media without compromising the main purpose of sago palm. The development of novel commodities from sago frond will change the perspective of the farmers and smallholders to appreciate sago palm as a highly profitable industrial crop producing high value product.